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Differential psychology 









Individual and Group Differences 
in Behavior 


Chairman^ Department of Psychology , 
tytcens College, New York 





Published May, 1937. Reprinted January, 1:939 ; 
May, 1940. 



The present book was written with three major aims 
in mind. In the first place, differential psychology is 
here presented, not as a separate field of psychology, but 
as one approach to the understanding of behavior. Its 
fundamental problems are no different from those of 
general psychology. It is apparent that if we can explain 
satisfactorily why individuals react differently from each 
other, we shall understand why each individual reacts as 
he does. The data of differential psychology should help 
to clarify the fundamental mechanisms of behavior in 
general. It is from this point of view that the problems 
of individual and group differences are surveyed in the 
present text. 

A second aim of the book has been to coordinate the 
various topics which have heretofore been loosely joined 
together under the caption of "individual differences." 
With the rapid increase in material on any one of these 
topics, there has appeared a tendency to regard each 
segment as an independent field of investigation. The 
mutual interrelation of the various problems has become 
obscured by the accumulation of data at a more rapid 
rate than it could comfortably be assimilated. It is an 
undoubted fact that the various branches of differential 
psychology have undergone a phenomenal development 
during the past two decades. This has resulted in an 
increasing specialization of interest among research work- 
ers and a frequent disregard of the broader implications 
of the data. Many apparently unrelated aspects of differ- 
ential psychology can profitably be considered together. 


Thus the data on such questions as familial resemblance, 
the relationship between mental and physical traits, the 
growth of abilities, and the organization of mental traits 
can be shown to have a mutual bearing upon each other. 
The writer has endeavored to bear constantly in mind the 
interrelationships among different types of investigations 
and has attempted to present a systematic organization 
and integration of the material. 

Finally, it has been our aim to report the major data 
and conclusions of differential psychology in a form suit- 
able for the college student. The present book has, in 
fact, grown out of a course in differential psychology 
which the writer has taught at Barnard College since 
1930. Much of the material of differential psychology has 
heretofore been available only in journal articles and 
highly technical books. Consequently, certain topics have 
been customarily omitted or touched upon lightly in dis- 
cussions of individual differences, being considered too 
" difficult" for the elementary student. Mental organ- 
ization is a good example of such a topic, although by 
no means the only one. Even the more advanced student 
of psychology who has specialized in other phases of the 
subject often finds it impossible to keep informed on 
current developments in certain branches of differential 
psychology. The writer believes that a non-technical and 
easily comprehensible presentation of such material is 
both feasible and desirable. An understanding of the 
basic concepts and major findings of any problem need 
not be limited to those who have mastered its specialized 

The present book could serve either as a text in special 
courses on differential psychology and "individual differ- 
ences" or as a supplementary text in such courses as 
general, applied, or educational psychology, and mental 



testing. It also provides relevant material for courses in 
social psychology. 

There is at present a growing interest in the origin of psy- 
chological differences among individuals and especially 
among groups. Many of the problems of differential psy- 
chology have become the subject of frequent popular dis- 
cussion and controversy. Thus the subject matter of this 
branch of psychology should prove intrinsically valua- 
ble. Moreover, as has already been pointed out, famili- 
arity with the main principles of individual variation will 
strengthen the student's understanding of general psy- 
chology. Lastly, the analysis of the problems and difficulties 
encountered in the investigation of individual differences 
should foster a critical attitude towards all data on these 
questions. Throughout the present book, special emphasis 
has been placed upon the examination of common sources of 
errors and pitfalls in the interpretation of obtained facts. 
We have thus hoped to provide the student with certain 
tools whereby he may evaluate for himself a set of data 
with which he is confronted. It seemed to the writatrthat 
this was more valuable than a mere compendium of facts. 
The development of critical ability and of a dispassionate 
and objective attitude towards human behavior is an 
urgent need in a world of rapidly changing values. 

The .writer is indebted to Prof. H. L. Hollingworth of 
Barnard College for a critical reading of the manuscript 
and for many stimulating comments. She wishes to 
acknowledge the invaluable assistance of Dr. J. P. Foley, 
Jr., of The George Washington University for an inten- 
sive reading of the entire manuscript in its early stages 
and for countless specific suggestions. Grateful acknowl- 
edgment is also made to the many authors whose works 
have been quoted in this book and especially to those 
who have made accessible to the writer unpublished data 


from their investigations. Finally, thanks are extended 
to the various publishers who have generously granted 
permission for the reproduction of figures and quotations 
from their publications. In all of these cases, specific 
acknowledgment has been made in the appropriate places. 

April, 1937 





Individual Differences in Pre-experimental Psycho- 
logical Theory 5 

The Personal Equation in Astronomy 9 

The Rise of Experimental Psychology .... 10 

Galton and the Biological Influence ...... n 

Early Experimentation with Tests 13 

Beginnings of Differential Psychology 16 

Intelligence Testing 18 

Group Testing 21 

The Measurement of Personality 23 

Current Trends in Differential Psychology ... 24 


The Distribution of Individual Differences ... 30 

The Normal Curve 32 

Other Types of Distribution Curves and What They 

Mean 35 

Some Typical Distributions 42 

Extent of Variability in Different Traits .... 51 

Individual Differences in Infrahuman Groups . . 57 


Fundamental Concepts . 67 

Prenatal Environment Ji 

Experimentally Produced Variations in Behavior. , 74 

Human Children Reared in Abnormal Environments 77 

Differences among Social or Occupational Groups . 83 




The Families of Eminent Men 97 

Degenerate Families 101 

Parent-Child Resemblance 106 

The Comparison of Siblings no 


The Psychological Study of Twins 119 

Twin Resemblances in Mental Traits 121 

Case Studies of Identical Twins Reared Apart . . 125 

Foster Children 129 


Experiments on Infant Development 140 

The Effects of Special Training and Coaching upon 

Mental Test Performance 145 

The Problem of Practice and Individual Differences 149 
Typical Experimental Findings on Practice and Vari- 
ability ..... 156 


The Growth Curve 161 

Adult Intelligence 170 

Adult Learning 175 

Training and Growth . 1 80 



Cranial Measurements 187 

Facial Characteristics 191 

Body Build , 196 

Physiological Conditions 203 

Sensory Defects 210 

General Evaluation 215 


Type Theories 222 

Implications of Type Psychology 230 



Evidence from Abnormal Cases 234 

Correlational Studies on Normal Groups .... 242 

Investigations on "Pure Types" 246 


The "Idiot Savant" 260 

Asymmetry of Development in "Normal" Indi- 
viduals 265 

The Individual Psychograph 269 

The Measurement of Trait Variability .... 280 

Evidence from Correlation 285 

Major Contemporary Theories of Mental Organiza- 
tion 299 

Methodological Problems 305 

Group Factors 311 

Form versus Content 313 

Shifting Components of Mental Life 315 

The Role of Environment 318 



Historical Views of Mental Disorder 329 

The Concept of Abnormality 331 

The Feebleminded 334 

The Insane 340 

The Neurotic 344 

Abnormality in Different Cultures 348 

Abnormality in Infrahuman Organisms .... 350 

The Nature of Abnormality 351 


Theories on the Nature of Genius 357 

Methods Employed in the Study of Genius . . 362 



Surveys of Adult Genius ........ 365 

The Early Mental Traits of Genius 370 

The Child Prodigy 373 

Mental Tests and the Superior Child 376 

Subsequent Careers of Intellectually Gifted Children ' 380 


PROBLEMS . . . 386 

Sex Differences in Achievement 387 

Sex Differences in Variability 390 

Selective Factors 394 

Relative Maturity 396 

Reliability of a Group Difference ...... 399 

Overlapping 402 

Nature of the Measuring Instrument 404 

Sex Differences and Culture 407 



Sensory Acuity and Motor Ability 415 

Special Aptitudes 417 

General Intelligence 425 

Scholastic Achievement 428 

Interests, Preferences, and Attitudes 432 

Character Traits 436 

Emotional Adjustment 439 

A " Masculinity-Femininity" Index of Personality 

Traits 443 


What Is a Race? ."...." 454 

Evaluation of the Criteria of Race ..... 458 

A Tentative Classification of Racial Groups . . . 461 

National and Linguistic Groupings 464 

Race Mixture "463 

Psychological Studies of Hybrid Groups .... 468 

Immigrant Groups - 475 




Language Handicap 483 

Difficulties of Test Administration 490 

Educational Differences 492 

Social and Economic Status 495 

General Cultural Milieu 497 

Traditions, Customs, and Interests 503 

The Criterion of Intellectual Superiority .... 508 

The Comparative Achievements of Different Races 512 



The Army Data 518 

"Natio-Racial" Differences among Children of Immi- 
grant Groups 523 

Cross-Comparisons among Racial and National 

Groups in Europe 527 

Race versus Culture in the Development of Person- 
ality Traits . . , 53 1 

Gesture: An Example of Culturally Conditioned Be- 
havior 538 

General Evaluation 543 

TIONS 548 

Theories of Urban-Rural Differences in Intelligence 551 
Mental Test Surveys of Rural Schoolchildren . . 554 
City and Country Differences in Europe .... 557 
The Intelligence of Mountain Children .... 560 
The Specificity of Intellectual Differences . . . 565 
The Mental Development of Farm Children . . . 572 
Some Data on Selective Migration versus Environ- 
mental Handicap 574 



Structure and Function 581 

Experiential Determination of Behavior . ... . 583 



Specificity of Behavioral Development , 588 

"Normal" and " Natural" Behavior ..... 595 

Nature and Variety of Psychological Groups . , . 598 

The Meaning of Individuality 601 




No topic has greater significance for the organization 
of life among human beings than that of the nature and 
basis of the individual differences among those human 
beings. Except for individual differences among us there 
would be no such distinctions as right and wrong; just 
and unjust; health and illness. There would be no laws, 
no courts, no systems of ethics; no politics and no need 
of government. Individual differences are responsible 
for such institutions as education, for such episodes as 
wars, and probably, if the truth were known, for culture, 
for science, for the church, and for nearly everything 
else that is characteristically human. 

Another striking fact is the way in which activities 
and institutions, springing from human individual differ- 
ences, become in turn responsible for further differentia- 
tion and variation. There can be no doubt that human 
diversity in some characteristics is biological in origin, 
and that to some extent we are different one from an- 
other because of the different stocks from which we spring 
and because of the multitudinous influences that make 
variation intrinsic to all living things. It is still true that 
"Men do not gather grapes of thorns nor figs of thistles." 

It is equally true that much of human diversity, es- 
pecially in the more subtle psychological traits, is a re- 
flection of the incidence of differential environmental 
effects. Theories of the basis of individual differences 
themselves exhibit variation. They range from a dogmatic 
hereditarianism, with a somewhat aristocratic air of de- 
terminism, through sane and balanced recognitions of 




Man has always been aware of differences among his 
fellow-beings. He has, to be sure, entertained various 
theories, beliefs, or superstitions regarding the causes of 
such differences, and has interpreted them differently 
according to his own traditional background, but he has 
at all times accepted the fact of their existence. Among 
primitive -peoples, unusual deviations in behavior are 
clearly recognized, , Thus many primitive groups acknowl- 
edge exceptional - artistic talent among their members 
and encourage the development of --specialized artists. 
The presence of hysterical or epileptoid symptoms, para- 
noid trends, and similar peculiarities of behavior has 
frequently been regarded' as an index of religious or magi- 
cal powers and has been treated accordingly. The history 
of religion is replete with* such instances. At any level 
of cultural development, specialization of labor itself im- 
plies a tacit assumption of differences -among people. 

Nor is this response, to individual -differences limited 
to the human species. Instances from inf rahuman behavior 
caritTcadily be found. The acceptance of .-certain.' individut 
ab'-as "leaders' 4 -by herds -.of elephants, buffaloes, and 
similar .-gxegariotis animals tes -been:- widely ;discussed in 
the literature. both of feet and driiction.: In, "communities 
of baboons, .^fceitain member is posted .'as /c sentinel" to 
watch for the approach :of. danger -and" warn the others 
by conventional -cries. "The frequently- -described "hack- 
ing" or hen-pecking behavior of chickens is another case 
in point* A definite -relationship of social domination is 



often displayed by chickens In the barnyard, this fighting 
or "hacking" behavior usually centering about the ac- 
quisition of food. In such cases, A will attack B 3 although 
the reverse will not occur. Violent conflicts often ensue 
when the authority of the chief "hacker" in the group is 
disputed. These and many other examples all serve to 
suggest a widespread differential response to individuals 
within a group. 

The objective and quantitative investigation of indi- 
vidual differences in behavior phenomena is the domain 
of differential psychology. What is the nature and extent 
of such differences? What can be discovered as to their 
causes? How are the differences affected by training, 
growth, physical conditions? In what manner are the 
differences in various traits related to one another, or 
organized? These are some of the fundamental questions 
raised by differential psychology and will be treated in 
Part I of the present book. 

Differential psychology is also concerned with an 
analysis of the nature and characteristics of major tradi- 
tional groupings, such as the subnormal and the genius, 
the sexes, and racial, national, and cultural divisions* 
This furnishes the subject-matter of Part II. The study 
of such group differences serves a threefold purpose. In 
the first place, one cannot ignore the fact that such group- 
ings are being made in the practical realm of everyday 
life. These distinctions cannot be swept away casually 
on the grounds that, perhaps, the study of individual 
differences reveals no need for them or -for any sharp 
divisions into clear-cut categories. Certain groups are 
recognized and responded to as distinctive in our present- 
day society. For a purely practical reason, therefore, 
these groups must be investigated, in the hope that the 
specific findings may throw some light upon their nature 


and possibly further a more intelligent practical under- 
standing of them. 

Secondly, the comparative investigation of different 
groups should help to clarify the fundamental problems 
of individual differences in general. In such groups we 
can see the principles of individual differences in operation 
and can note their effects. Group differences in behavior, 
when considered in conjunction with other concomitant 
differences among the groups, furnish an excellent avail- 
able means of analyzing the causes of variability. 

Thirdly, the comparison of a psychological phenomenon 
as it occurs in different groups may contribute towards a 
clearer understanding of the phenomenon itself. The find- 
ings of general psychology, when tested in widely varying 
groups, are sometimes found to be not so general as was 
supposed. To study a phenomenon in all its varied 
manifestations is to have a better grasp of its essential 

Notwithstanding the early and widespread recognition 
of individual differences in the practical adjustments of 
everyday life, the systematic investigation of such differ- 
ences is a relatively recent development in psychology. 
A brief historical survey of theories as well as investiga- 
tions in the field of differential psychology will be given. 


One of the earliest instances of explicit recognition of 
individual differences is to be found in the Republic of 
Plato. A fundamental aim of Plato's ideal state is, in 
fact, the assignment of individuals to the special tasks 
for which they are suited. In Book II of the Republic 
appears the following statement: "Really, I said, it is 
not improbable; for I recollect myself, after your answer, 


that, In the- first place, no two persons are born exactly 
alike, but each differs from each in natural endowments, 
one being suited for one occupation and another for an- 
other" (21, p. 60). 1 Plato proposes a series of "actions 
to perform " for use as tests of military aptitude on those 
who are to be the soldiers of his ideal state. These actions 
are designed to sample the various traits considered essen- 
tial to military prowess, and represent the first systematic 
description of an aptitude test on record. 

Nor did the versatile genius of Aristotle overlook indi- 
vidual variation. He discusses at some length group 
differences, including species, racial, social, and sex differ- 
ences in mental and moral traits. In many of his works 
there is also an implicit assumption of individual differ- 
ences, although it is interesting to note that Aristotle 
does not offer any extensive treatment of these differences 
as such. One gets the impression that he regards the exist- 
ence of individual variation as too obvious to need special 
mention. That he attributes such differences at least in 
part to innate factors seems to be indicated by a number 
of statements such as the following: 

Perhaps, then, some one may say, "Since it is in my 
power to be just and good, if I wish I shall be the best of 
all men/' This, of course, is not possible. . . . For he who 
wills to be best will not be so, unless Nature also be presup- 
posed (i, Magna Moralia, ir87 b ). 

Throughout the several Ethics of Aristotle, there appear 
passages which imply individual variation- The follow- 
ing statement, for example, leaves little doubt regarding 
Aristotle's position on this point* 

After these distinctions we must notice that in everything 
continuous and divisible there is excess, deficiency, and the 

1 The numbers in parentheses refer to the numbered References at the end 
of the chapter. 


mean, and these In relation to one another or in relation to 
us, e.g., in the gymnastic or medical arts, and in those of 
building and navigation, and in any sort of action, alike 
scientific and non-scientific, skilled and unskilled. For mo- 
tion is continuous, and action is motion (i, Ethica Eudemia, 

I22O b ). 

Aristotle then proceeds to describe the characteristics of 
men possessing an excess or a deficient amount of various 
traits such as irascibility, audacity, shamelessness, and 

In the Scholasticism of the Middle Ages, individual 
differences were completely neglected. The individual 
as such had no part in the doctrines and generalizations 
of the Schoolmen. Rationalistic methods persisted even 
longer in the study of mental life than in other disciplines, 
where empiricism was gradually making itself felt. The 
keen observation of the ancients which had led to the 
discovery of many facts about human traits and behavior 
was now subordinated to religious speculation. The logical 
techniques of the Greeks were being employed primarily 
to build elaborate justifications for current theological 
dogmas. The spread of Christianity itself, with its em- 
phasis upon otherworldliness and spiritual equality, was 
also doubtlessly influential in turning attention away from 
the individual 

The many varieties of Associationism which flourished 
from the seventeenth to the nineteenth centuries likewise 
took little heed of individual differences. It was with the 
elaborate mechanics whereby ideas become associated, 
giving rise to complex mental processes, that the associa- 
tionists were primarily concerned. Their statements were 
general principles with no allowance for individual varia- 
tion. Bain, the last of the so-called pure associationists, 
does, however, give some attention to individual differ- 


ences in his writings. The following passage is taken 
from his book on The Senses and the Intellect (1855). 
"There is a natural force of adhesiveness, specific to 
each constitution, and distinguishing one individual from 
another. This property, like almost every other assign- 
able property of human nature^ 1 consider to be unequally 
distributed" (2, p. 237). 

A simultaneous development in educational theory 
should probably be included at this point. In the writ- 
ings and practices of a group of "naturalist 1 " educators 
of the late eighteenth and early nineteenth centuries, 
including Rousseau, Pestalozzi, Herbart, and Froebel, 
there is found a definite shift of interest to the individual 
child (cf. 1 6). Educational policies and methods were 
to be determined, not by external criteria, but by direct 
observation of the child and his capacities. The emphasis 
still seemed to be, however, on the observation of the 
individual as representative of individuals in general, 
rather than as distinct from other individuals* Although 
statements can be found in the writings of these educators 
to the effect that individuals differ and that their educa- 
tion should be adapted to these differences, still the 
emphasis is laid more heavily upon free 3 "natural" edu- 
cation in contrast to externally and arbitrarily imposed 
procedures, rather than upon individual differences them- 
selves. The term "individual" is often used to mean 
simply "human nature." 

Finally, mention may be made of the various treatises 
on race and racial psychology which appeared in the late 
eighteenth and early nineteenth centuries. Discussions 
of race differences are to be found in the works of such 
writers as Buffon, Herder, and de Gobineau, the last 
having been especially influential in determining subse- 
quent popular beliefs about race. 


Curiously enough, the first systematic measurements 
of individual differences were undertaken not in psychol- 
ogy but in the old and time-honored science of astronomy. 
In 1796, Maskelyne, the astronomer royal at the Green- 
wich Observatory, dismissed Kinnebrook, his assistant, 
because the latter observed the times of stellar transits 
nearly a second later than he did. The method employed 
at the time to make such observations was the "eye and 
ear" method. This method involved not only coordination 
of visual and auditory impressions, but also rather com- 
plex spatial judgments. The observer noted the time to 
a second on the clock, then began to count seconds 
with the heard beats of the clock, at the same time 
watching the star as it crossed the field of the telescope. 
He noted the position of the star at the last beat of the 
clock just before it reached the " critical" line in the field; 
then, similarly, he noted its position with the first beat 
immediately after it had crossed that line. From these 
observations, an estimate was made in tenths of a second 
of the exact time when the star crossed the critical line. 
This was the accepted procedure and was regarded as 
accurate to one- or two-tenths of a second. 

In 1816, Bessel, astronomer at Konigsberg, read of the 
Kinnebrook incident in a history of the Greenwich Astro- 
nomical Observatory, As a result, he became interested 
in measuring what came to be known as the "personal 
equation" of different observers. Originally, the personal 
equation referred to the difference in seconds between the 
estimates of two observers. Bessel collected and published 
data on several trained observers, and pointed out not 
only the presence of such a personal equation or error 
when comparing any two observers, but also the variabil- 
ity in the equation from -time to time. This represents 


the first published record of quantitative data on indi- 
vidual differences. 

Many astronomers followed up BessePs measurements. 
In the latter half of the nineteenth century, with the 
introduction of chronographs and chronoscopes, it became 
possible to measure the personal equation of a given 
observer without reference to any other observer. The 
attempt was made to reduce all observations to their 
objectively correct values without reference to a system 
of time based upon one observer as a standard. Astrono- 
mers also undertook an analysis of the various conditions 
which affected the size of the personal equation. It was 
this latter problem, rather than the measurement of indi- 
vidual differences, which was taken up by the early experi- 
mental psychologists in their studies of "reaction time." 


During the latter half of the nineteenth century, psy- 
chology began to venture away from its armchair and 
enter the laboratory. Most of the early experimental 
psychologists were physiologists whose experiments gradu- 
ally came to take on a psychological tinge. As a result, 
both the viewpoints and the methods of physiology were 
frequently carried over directly into the infant science 
of psychology. In 1879, Wilhelm Wundt established the 
first laboratory of experimental psychology at Leipzig. 
Experiments of a psychological nature had been per- 
formed previously by Weber, Fechner, Helmholtz, and 
others, but Wundt's laboratory was the first to be devoted 
exclusively to psychology and to offer facilities for train- 
ing students in the methods of the new science. Students 
from many parts of the world were attracted to Wundt's 
laboratory, and upon their return founded laboratories 
in their own countries. 


The problems investigated in these early laboratories 
testify to the close kinship of experimental psychology 
with physiology. The psychology of visual and auditory 
sensation, reaction time, psychophysics, and association 
constituted nearly the entire field of experimentation. 
It was characteristic of the early experimental psycholo- 
gists either to ignore individual differences or to regard 
them in the nature of experimental "errors." The greater 
the individual variation in a phenomenon, the less ac- 
curate would be the general laws discovered in regard to 
it. Thus the extent of individual differences represented 
the " probable error " to be expected in the operation of 
the general laws whose formulation was the only aim of 
the experimental psychology of this period. 

It is apparent that the rise of experimental psychology 
shifted the emphasis away from the study of individual 
differences rather than towards it. Its one contribution 
to the development of a differential psychology is to be 
found in its demonstration that psychological phenomena 
are amenable to objective and even quantitative investiga- 
tion, that psychological theories can be tested by actual 
data, that psychology, in short, could become an empirical 
science. Such a step was required before theories about 
the individual could be replaced by studies on individual 


With the spread of Darwinism in the late nineteenth 
century, psychology became consistently more biological 
in its approach. One of the most widely known of Dar- 
win's followers was Sir Francis Galton, who first attempted 
to apply the evolutionary principles of variation, selection, 
and adaptation to the study of human individuals. Gal- 
ton's scientific pursuits were many and varied, but they 


were unified by an underlying interest in the study of 
heredity. The science of Eugenics, whose aim is the 
control and direction of human evolution, was originated 
by Gal ton. In 1869, he published a book entitled Hmdi** 
tary Genius, in which, by the application of the now 
well-known family history method, he tried to demon- 
strate the inheritance of specific talents in various fields 
of work. In connection with the study of human inherit- 
ance, it soon became apparent that related and unrelated 
individuals must be measured, objectively and in large 
numbers, in order to discover the degrees of resemblance 
among them. For this purpose, Galton devised numerous 
tests and measures and in 1882 established his famous 
anthropometric laboratory at South Kensington Museum 
in London. There, for the payment of a small fee, indi- 
viduals could be tested in sensory discrimination,, motor 
capacities, and other simple processes. 

Through the measurement of sensory processes, Galton 
hoped to arrive at an estimate of the subject's intellectual 
level. In the Inquiries into Human Faculty, a collection 
of miscellaneous essays published in 1883, he wrote: "The 
only information that reaches us concerning outward 
events appears to pass through the avenue of our senses; 
and the more perceptive the senses are of difference, the 
larger is the field upon which our judgment and intelligence 
can act" (9, p. 27). And again, on the basis of findings 
on the inferior sensitivity of idiots, he observes that this 
sensory discriminative capacity "would on the whole be 
highest among the intellectually ablest*' (9, p. 29). For 
this reason, measures of sensory capacity, such as vision 
and hearing, constituted a relatively large portion of the 
tests which Galton constructed and employed. Among 
these tests may be mentioned the Galton bar for visual 
discrimination of length, the Galton whistle for the de- 


termination of the highest audible pitch, kinsesthetic dis- 
crimination tests based on the arrangement of a series 
of weights, as well as tests of strength of movement, speed 
of simple reactions, and many others of a similar nature. 

Galton also initiated the use of "free association" tests, 
a technique which was subsequently adopted and followed, 
up by Wundt. Galton's study of mental imagery is well 
known and represents the first extensive psychological 
use of questionnaire methods. In this questionnaire, 
the subject was directed "to think of some definite ob- 
ject- suppose it is your breakfast table as you sat down 
to it this morning and consider carefully the picture 
that rises before your mind's eye" (9, p. 84). They were 
then to describe the picture with reference to illumination, 
definition, and coloring. Wide individual and group 
differences were revealed by this analysis of imagery. 

A further and very significant contribution of Galton 
to differential psychology was his development of statis- 
tical methods for the analysis of the data of individual 
differences. Formerly, statistics had been chiefly the 
tool of the trained mathematician and the professional 
gambler. Statistical techniques were not available in a 
form which would enable the mathematically untrained 
worker in the biological sciences to employ them. Galton 
realized the need for such techniques and developed many 
of the statistical procedures in current use today. This 
phase of his work has been extended and increased in 
scope by many eminent students, chief among whom is 
Karl Pearson, who succeeded Galton as director of the 
anthropometric laboratory in 1911. 


The term "mental test" was first employed in 1890 
by Cattell, in an article entitled Mental Tests and Measure- 


menls (6). James McKeen Cattell was an American 
student of Wundt. In 1888, having obtained his doctorate 
at Leipzig, he returned to this country, where he was in- 
strumental both in the spread of experimental psychology 
and in the development of mental testing. He was 
influenced by Galton's work in test construction and 
statistics. In Cattell, we find a convergence of two con- 
temporary movements in psychology, the rise of the ex- 
perimental method and the measurement of individual 
differences. It was characteristic of all of the early 
American mental tests that they developed in the psy- 
chological laboratory and partook of the nature of the 
experimental psychology of the time. This was not true 
of many of the tests developed in other countries. 

In addition to his experiments on reaction time, atten- 
tion span, controlled association, reading, psychophysics, 
and similar problems, Cattell constructed a series of tests 
which were administered for many years to freshmen and 
seniors at Columbia College. This series included the 
following tests: 1 (i) strength of grip; (2) rate of arm 
movement; (3) two-point threshold on the back of the 
hand; (4) amount of pressure required to produce pain 
on the forehead; (5) least noticeable difference in weights; 
(6) reaction time to sound; (7) speed of color naming; 
(8) bisection of a 50-011. line; (9) reproduction of a 10 
second time interval; (10) auditory memory span for 
letters. This list is reproduced in full since it is typical 
of the various test series which appeared at the time. 

In 1891, Miinsterberg (17) described a series of tests 
which he had employed on schoolchildren. Tests of 
reading, controlled association of various sorts, judgment, 
memory, and other simple mental processes were included. 
At the 1893 Columbian Exposition at Chicago, Jastrow 

1 For a fuller description, cf. Cattell and Farrand (7). 


administered a series of sensory, motor, and simple per- 
ceptual tests to all persons interested. Norms of physical 
growth and mental development were presented with the 
tests (cf. 20). 

What is probably the first attempt to evaluate test 
scores in terms of an independent criterion is to be found 
in the study by Bolton (4) reported in 1892. Bolton 
analyzed data collected by Boas on about 1500 school- 
children. The children's memory spans were compared 
with their teachers' estimates of " intellectual acuteness," 
very little correspondence being found. Gilbert (10), 
in 1893, compared teachers' estimates of " general ability" 
on some 1200 children with their scores on eight tests 
of sensory and motor functions, reaction time, sensory 
memory, and suggestibility. Three years later, Gilbert (n) 
described some additional tests and reported the results 
obtained with them on several hundred children. The 
data were analyzed in respect to sex differences, intel-, 
lectual growth, and the relationship of mental and physical 

In Germany, Oehrn (19), a pupil of Kraepelin, pub- 
lished in 1889 the results of an intensive study of a series 
of tests on ten subjects. The tests had been rather arbi- 
trarily selected to measure perception, memory, associa- 
tion, and motor functions. In 1895, Kraepelin (15) pro- 
posed a set of traits which he regarded as basic in the 
characterization of any individual. He also devised tests 
for the measurement of these traits, most of the tests 
involving simple arithmetic operations. These tests were 
of rather dubious validity for measuring the traits in 
question, and in addition they were quite impracticable, 
some of them requiring several days for their completion. 
Research on mental tests was also being conducted simul- 
taneously under the direction of the Italian psychologist 


Ferrari. In an article appearing in 1896, some of these 
tests were described (12). They included measures of 
vasomotor activity, motor strength and skill, range of 
apprehension, description of pictures, and temporal esti- 
mation. Interesting individual differences were reported 
in many of these tests. 


At the turn of the century, differential psychology had 
begun to assume very definite shape. In 1895, Binet and 
Henri published an article entitled La psychologie indi- 
vidudle (3), which represents the first systematic analysis 
of the aims, scope, and methods of differential psychology. 
Their opening sentence suggests the status of this branch 
of psychology at the time. It reads: "We broach here 
a new subject, difficult and as yet very meagerly explored" 
(p. 411). Binet and Henri put forth as the two major 
problems of differential psychology, first, the study of the 
nature and extent of individual differences in psychologi- 
cal processes; and secondly, the discovery of the interrela- 
tionships of mental processes within the individual, so that 
we may arrive at a classification of traits and determine 
which are the more basic functions. 

In 1900 appeared the first edition of Stern's book on 
differential psychology, under the title Uber Psychologie 
der indimduellen Differ enzen (25). Part I deals with the 
nature, problems, and methods of differential psychology. 
Within the scope of this branch of psychology Stern 
included differences among individuals as well as among 
racial and cultural groups, occupational and social levels, 
and the two sexes. The fundamental problem of differ- 
ential psychology he characterized as threefold: (i) What 
is the nature and extent of differences in the psychological 
life of individuals and groups? (2) What factors deter- 


mine or affect these differences? in this connection he 
mentioned heredity, climate, social or cultural level, train- 
ing, adaptation, etc. (3) How are the differences mani- 
fested? Can they be detected by such indices as hand- 
writing, facial conformation, etc.? Stern also included a 
discussion of the concepts of psychological type, individu- 
ality, and normality and abnormality. Under methods 
of differential psychology, he gave an evaluation of intro- 
spection, objective observation, the use of material from 
history and poetry, the study of culture, quantitative 
testing, and experiment. Part II contains a general 
discussion and certain data on individual differences in 
various psychological traits, from simple sensory capac- 
ities to more complex mental processes and emotional 
characteristics. Stern's book appeared in a highly re- 
vised and enlarged edition in 1911, and again in 1921, 
under the title of Differentielle Psychologic in ihren metho~ 
dischen Grundlagen (26). 

In America, committees were being appointed to in- 
vestigate testing methods and to sponsor the accumula- 
tion of data on individual differences. At its 1895 meet- 
ing, the American Psychological Association appointed a 
committee "to consider the feasibility of cooperation 
among the various psychological laboratories in the col- 
lection of mental and physical statistics " (7, p. 619). In 
the following year, the American Association for the 
Advancement of Science established a standing committee 
to organize an ethnographic survey of the white population 
in the United States. Cattell, one of the members of this 
committee^ pointed out the importance of including psy- 
chological tests in this survey and suggested that its 
work be coordinated with that proposed by the American 
Psychological Association (7, pp. 619-620). 

The application of the newly devised mental tests to 


various groups was also getting under way, R. L. Kelly 
(13) In 1903 and Norsworthy (18) In 1906 compared 
normal and feebleminded children on sensori-motor and 
simple mental tests, and called attention to the continuous 
gradation in ability which exists between these groups, 
the feebleminded not constituting a distinct category. In 
1903 appeared Thompson's The Mental Traits of Sex (28), 
the result of several years' testing of men and women 
with a variety of tests. This represents the first compre- 
hensive investigation on sex differences. Tests of sensory 
acuity, motor capacities, and a few simple mental proc- 
esses were also being administered for the first time to 
various racial groups. A few scattered investigations ap- 
peared before 1900. In 1904 Woodworth (30) and Bruner 
(5) tested several primitive groups at the St. Louis Ex- 
position. In the same year appeared Spearman's original 
article putting forth his Two-Factor theory of mental or- 
ganization and introducing a statistical technique for In- 
vestigating the problem. Thus, shortly after the begin- 
ning of the century, the foundations had been laid for 
every branch of differential psychology. 


The intelligence test Is a product of the twentieth 
century. The early mental tests were predominantly 
sensori-motor or very simple in nature. This was no 
doubt a carry-over from the sensationism current in the 
psychological laboratories of the time. Complex mental 
processes were believed to be best understood by an- 
alyzing them into their elementary components, usually 
of a sensory nature. Most of the efforts of the early 
experimentalists were therefore devoted to the study of 
sensations and simple reactions, and this influence left 
its mark on the newly developing mental tests. 


Binet and Henri, in their 1895 article (3), were the first 
definitely to point out the need for more complex tests 
to measure " intelligence." They examined the five most 
comprehensive current test series, those of Cattell, Miin- 
sterberg, Jastrow, Kraepelin, and Gilbert, and found all 
of them greatly overweighted with sensory tests and 
lacking in tests of complex processes. From an analysis 
of the available data, they concluded that individual 
differences are more marked in complex tasks and that 
the latter are therefore better suited to the study of such 
differences. Partly to remedy this deficiency in the cur- 
rent tests, Binet and Henri described ten types of tests 
which in their opinion would yield the largest and most 
significant individual differences. The series included 
tests of memory, mental imagery, imagination, attention, 
comprehension, suggestibility, aesthetic appreciation, moral 
feelings, muscular force and force of will, and motor abil- 
ity and visual discrimination. The entire series, according 
to the authors, would require only from one to one and 
one-half hours. 

In 1897, Ebbinghaus (8) proposed a theory to the effect 
that intelligence is the ability to combine or integrate 
the items of experience, and offered the sentence com- 
pletion test as a technique for measuring this ability. 
In this test, the subject is presented with sentences in 
which certain of the words are missing and he is required 
to fill in the proper words. In experiments on German 
schoolchildren, Ebbinghaus had found this test more ef- 
fective than simpler tests of calculation and memory. 
The completion test showed the most regular increase in 
score with age and it was also the only one of the tests 
employed which differentiated clearly among those pupils 
within each grade whose scholastic standing was good, 
average, or poor. Binet's contention for the superiority 


of the more complex tests In differential psychology was 
+k u s corroborated. 

Two American studies of this period lent further sup- 
port to Binet's statements. One of these studies (22) 
was conducted by Sharp, a student of Titchener, and was 
designed as a specific investigation of the conclusions of 
Binet and Henri. A set of tests, modeled largely on those 
of Binet and Henri, was administered to seven advanced 
psychology students. The experiment was very intensive 
and included the repetition of similar tests on different 
days to determine the consistency of the processes tested. 
In general, although the need for further controls and 
refinements was suggested, the tests proved satisfactory 
and yielded sizable individual differences in spite of the 
homogeneous and select nature of the group. Sharp 
concluded: "We concur with Mm. Binet and Henri in 
believing that individual psychical differences should be 
sought for in the complex rather than in the elementary 
processes of mind, and that the test method is the most 
workable one that has yet been proposed for investigat- 
ing these processes" (22, p. 390). A few years later, 
Wissler (29) published the results of his correlation anal- 
ysis of the data collected in CattelPs laboratory. The 
correlations showed "little more than a chance relation " 
among the tests, and also a negligible correspondence 
with academic grades. Thus the inadequacy of the simple 
tests originally employed was again indicated. 

Against this background of theory and data appeared 
the first intelligence scale. In 1904 the French Minister 
of Public Instruction appointed a committee to investi- 
gate the causes of retardation among public schoolchil- 
dren. Binet was one of the members of this committee. 
As a direct outgrowth of his work in this connection, 
Binet published, in collaboration with Simon, the 1905 


scale for measuring Intelligence. This scale consisted of 
30 problems arranged in a rough order of difficulty. In 
1908 appeared Binet's first revision of the scale, in which 
the tests were grouped into age levels and the concept 
of "mental age" 1 was introduced. The scale was again 
revised in 1911, the year of Binet's untimely death. 2 

The Binet tests have been translated into more than a 
dozen languages and their use has spread over every con- 
tinent. In America, five different revisions have appeared, 
of which the most widely known are the Stanford-Binet, 
prepared by Terman and his associates at Stanford 
University, and the Kuhlman-Binet which extended the 
scale down to the three-months age level. The intelligence 
quotient (I.Q.)? found by dividing the child's mental 
age by his chronological age, was first employed in the 
Stanford-Binet, although its use and advantages had been 
previously discussed by Stern and others. The develop- 
ment of performance scales for testing the deaf, the 
illiterate, and the foreign, to whom language tests are 
inapplicable, may be mentioned as a further development 
of intelligence testing. 


The Binet scale and its revisions are "individual tests" 
in the sense that only one subject can be tested at a time. 
Furthermore, owing to the nature of these tests, a highly 
trained examiner is required to administer them. Testing 

1 The child's score on an age scale is expressed as a mental age (M.A.). If, 
for example, he passes successfully all of the tests assigned to the loyear level, 
he has a mental age of 10, regardless of what his chronological age may be. 

2 Attention has recently been called to the fact that as early as 1887 a series 
of developmental standards and simple tests for judging the mental level of 
infants during the first three years was worked out by an American physician, 
Dr. S. E. Chaille. The concept of mental age seems to have been implicit in his 
treatment of the data, although this term was not employed (cf. Goodenough, 
F. L., "An Early Intelligence Test," Child Dev., 1934, 5, 13-18). 


on a large scale could not be carried on under these 
conditions. Data on such problems as sex and race differ- 
ences, for example, which require the investigation of large 
samples, would be very slow in accumulating. 

The advent of the group intelligence scale was probably 
the chief factor in bringing about the popular mental 
testing fad. The group test is designed with a view to its 
general use. It is not only adapted to the simultaneous 
testing of large groups, but it is also relatively easy to 
administer and fool-proof in its scoring. The- impetus 
for the development of group tests was given by the 
pressing need of testing over one and one-half million 
men in the United States army in 1917. A quick, rough 
classification in respect to intelligence was necessary for 
many purposes. Discharge because of serious mental 
defect, assignment to labor battalions requiring only low- 
grade work, admittance to officers' training camps, and 
a number of similar problems required a knowledge of 
the intellectual level of the soldier. 

Accordingly, a committee was appointed by the Amer- 
ican Psychological Association to devise a test suited to 
this purpose. The committee consisted of five psycholo- 
gists who were specialists in mental testing, and was 
under the direction of Robert M. Yerkes. All of the 
available material on mental tests was examined for its 
suitability to the needs of the army testing program. The 
greatest assistance was derived from an unpublished group 
scale which had previously been developed by Otis, and 
which the latter made available to the government. The 
final outcome of the research of the army psychologists 
was the Army Alpha and the Army Beta. The former 
was the more widely used of the two; the latter is a non- 
language scale, and was designed for testing illiterates 
and foreigners unfamiliar with English. 


After the close of the World War, group tests were 
constructed at a rapid rate. Soon special tests were 
available for elementary schoolchildren as well as kinder- 
garten and pre-school levels, high school and college stu- 
dents, and unselected adults. Mental testing attained 
heretofore undreamed-of proportions. School teachers 
were now qualified to administer the newly simplified 
tests; large-scale school surveys were initiated; college 
freshmen were tested as part of the routine of admission; 
the general public became intelligence-test-conscious, and 
the I.Q. became a byword in everyday conversation. 

This sudden popularization and publicity was an un- 
fortunate handicap in the development of a measuring 
instrument still in its infancy. The intelligence scales 
were as yet very crude when they were put into the hands 
of the layman. They were too often accepted as a finished 
product and an infallible guide. Analysis of results and 
evaluation of techniques were subordinated to the more 
alluring occupation of classifying people. Occasionally 
psychologists themselves were guilty of over-hasty gen- 
eralization. Data on the various problems of differential 
psychology were being amassed in a rush. Sweeping 
conclusions were drawn and quoted. 


The extension of testing techniques from sensory and 
intellectual capacities to emotional and social traits is 
also a very recent development. An antecedent of current 
personality testing may be found in Kraepelin's first use 
of the free association test on pathological cases and on 
individuals who had been experimentally subjected to 
various influences such as fatigue, hunger, and drugs. 
Kraepelin (14) reported that all of these agencies increased 
the number of superficial associations. In 1894, Sommer 


(23) suggested that mental disorders could be differenti- 
ated by means of the free association test. The use of this 
test, for a variety of purposes, has persisted to the present. 

The most fruitful approach to the measurement of 
personality traits, however, has proved to be through 
standardized questionnaire and rating scale methods. 
These methods were originally developed by Gallon, 
Pearson, and Cattell in a different connection. The 
first widely employed personality questionnaire was the 
Woodworth "Personal Data Sheet" (cf. 27, Ch. V), an 
inventory of neurotic tendencies and emotional malad- 
justments devised for use on the American soldiers during 
the World War. This questionnaire was prepared by 
Woodworth, who was chairman of the Committee on 
Emotional Fitness appointed by the National Research 
Council. Although the armistice came before the final 
form of the questionnaire could be extensively applied, 
it was used subsequently in army hospitals and yielded 
much interesting information. 

Several revisions and adaptations of the Woodworth 
questionnaire have appeared, including forms especially 
suited for children, and for college students. Tests have 
also appeared for the measurement of various other so- 
cial and emotional characteristics, such as introversion- 
extroversion, ascendance-submission, and self-sufficiency. 
A fairly recent development is the construction of objec- 
tive " performance" tests of moral or character traits, 
such as honesty, cooperation, and self-control. Data on 
individual and, to a lesser extent, group differences are 
being steadily accumulated with all of these tests. 


After about twenty years of phenomenal development 
in the construction and application of mental tests, psy- 


chologists are beginning to turn their attention to a 
critical analysis of testing techniques themselves. There 
is apparent a growing tendency to question generaliza- 
tions, to scrutinize the conditions under which data were 
obtained, and to evaluate the results in the light of such 
conditions. A reaction is setting in against the indiscrimi- 
nate use of mental tests which followed the rise of group 
testing. In differential psychology, this reaction is mani- 
fested in two chief ways. In the first place, increasing 
stress is being laid upon the influence of environmental 
conditions in determining or modifying the individual's 
characteristics. In the second place, the measurement of 
"general intelligence" is losing its prominence as the goal 
of testing. Individual as well as group differences are 
being sought in narrower and more clearly definable traits. 

The original aim of the mental testers was the measure- 
ment of the individual's "capacities" or potentialities 
of intellectual development, as distinguished from his 
present skills and information. The measurement of the 
latter would have been a relatively simple task. If we 
wish to ascertain whether an individual is proficient in 
many languages, for example, we need only examine his 
knowledge of all languages with which he claims familiar- 
ity. But if we want to know whether this individual can 
learn languages easily, whether it would be worth while 
to teach him, or to advise him to enter a vocation which 
demands a mastery of several languages, then we are 
faced with a much more difficult problem. This was the 
type of problem with which the mental tester tried to cope. 

If one is to determine what the individual can do rather 
than what he has already accomplished, it was argued, 
it is necessary in some way to "rule out" differences in 
the previous experience or training of the subjects. This 
was attempted either by presenting material which was 


equally unfamiliar to all, or by the reverse procedure of 
utilizing only material common to everyone's experience. 
Frequently, the two methods were combined, as in the 
use of familiar material in a novel and unusual manner. 
Such a procedure is a practicable one and will yield useful 
information, provided its limitations and assumptions are 
kept clearly in view. In respect to the use of familiar 
material, it becomes necessary to ascertain that the ma- 
terial is actually familiar, in an approximately equal 
degree, to all of the subjects. A test is applicable only 
to individuals similar in their experiential background 
to the group upon whom it was standardized. When 
given to individuals from different national or cultural groups ', 
or from widely differing economic, social, or educational 
levels, "intelligence tests" do little more than reflect the 
varied backgrounds of the subjects. Under such conditions, 
the tests fail to fulfill the original purpose for which they 
were constructed. We are here concerned only in present- 
ing this point of view as a recent historical development; 
further elaboration of its theoretical implications will be 
found in subsequent chapters. 

The current trend toward the development of tests of 
separate traits and special aptitudes likewise results from 
a more searching analysis of testing methods. Recent 
research on the relationships among abilities suggests 
that important individual differences might be obscured 
if all abilities are lumped indiscriminately under the in- 
clusive concept of "general intelligence." From the prac- 
tical standpoint of prediction, tests of special aptitudes 
are being constructed to fit the needs of particular educa- 
tional or vocational situations. From the standpoint of 
theoretical interpretation, investigations on independent 
traits or unitary abilities are contributing towards a clearer 
understanding of individual and group differences. 



1. Aristotle. The Works of Aristotle^ ed. by W. D. Ross. Ox- 
ford: Clarendon Press, 1915. Vol. IX, Magna Moralia, 
Ethica Eudemia, de Virtutibus et Vittis. 

2. Bain, Alexander. The Senses and the Intellect. London: 
Parker, 1855. Pp- 614. 

3. Binet, A., and Henri, V. "La psychologic individuelle," 
Annee fsychoL, 1895, 2, 411-463. 

4. Bolton, T. L. "The Growth of Memory in Schoolchildren," 
Amer. J. Psychol., 1891-92, 4, 362-380. 

5. Bruner, F. G. "The Hearing of Primitive Peoples," Arch. 
Psychol., 1908, No. n. Pp. 113. 

6. Cattell, J. McK. "Mental Tests and Measurements," Mind, 
1890,15, 373"38&. 

7. Cattell, ]. McK., and Farrand, L. "Physical and Mental 
Measurements of the .Students of Columbia University," 
Psychol. Rev,, 1896, 3, 618-648. 

8. Ebblnghaus, H. "tJber eine neue Methode zur Priifung 
geistiger Fahigkeiten und ihre Anwendung bei Schulkin- 
dern/' Zscht. f. angew. Psychol., 1897, 13, 401-459. 

9. Galton, F. Inquiries into Human Faculty and Its Develop- 
ment. London: Macmillan, 1883. Pp.387. 

10. Gilbert, J. A. "Researches on the Mental and Physical 
Development of School Children," Stud. Yale Psychol. Lab., 
1894, 2, 40-100. 

11. - . "Researches upon Children and College Students," 
Iowa Univ. Stud. Psychol^ 1897, I, 1-39. 

12. Guiccardi, G., and Ferrari, G, C. "I testi mentali perl'esame 
degli alienati," Riv. sper. di freniatria, 1896, 22, 297-314. 

13. Kelly, R. L. "Psychophysical Tests of Mentally Deficient 
Children," Psychol. Rev*, 1903, 10, 34S~37 2 - 

14. Kraepelin, E. Uber die BeeinfiHssung einjacher pychischer 
Forgange durch einige ArmeimitteL Jena: Fischer, 1892, 
Pp. 259. 

j^ - m "Der psychologische Versuch in der Psychiatric," 
Psychol. Arbeiten, 1895, I, 1-91. 


16. Monroe, P. A Textbook in the History of Education. N. Y.: 
Macmillan, 1926. Pp. 759. 

17. Miinsterberg, EL "Zur Individualpsychologie," Centralblatt 
fur Nervenheilkunde und Psychiatrie, 1891, 14, 196-198. 

1 8. Nors worthy, N. "The Psychology of Mentally Deficient 
Children/' Arch. PsychoL, 1906, No. i. Pp. in. 

19. Oehrn, A. Experimented Studien zur Individualpsychologie. 
Dorpater Dissertation, 1889 (also publ. in PsychoL Arbeiten^ 

20. Philippe, J. "Jastrow Exposition d'anthropologie de 
Chicago Tests psychologiques, etc.," Annee PsychoL, 1894, 

21. Plato. The Republic of Plato (transl. by J. L. Davies and 
D. J. Vaughan). N. Y.: Burt, 19. Pp. 406. 

22. Sharp, S. E. "Individual Psychology: a Study in Psycholog- 
ical Method," Amer. J. PsychoL, 1898-99, 10, 329-391. 

23. Spmmer, R. Diagnostik der Geisteskrankheiten fur prakiische 
Arzte und Siudierende. Wien und Leipzig: Urban und 
Schwarzenberg, 1894. Pp. 302. 

24. Spearman, C. " * General Intelligence' Objectively Deter- 
mined and Measured," Amer. J. PsychoL^ 1904, 15, 201-293. 

25. Stern, W. Uber Psychologie der indwiduellen Diffmnzen 
(Ideen zur einer " Differ enzdlen Psychologic"}* Leipzig: 
Earth, 1900. Pp. 146. 

26. . Die Differentielle Psychologie in ihren methodischen 

Grundlagen, Leipzig: Earth, 1921. Pp. 545. 

27. Symonds, P. M. Diagnosing Personality and Conduct. 
N. Y.: Century, 1931. Pp. 602. 

28. Thompson, H. B. The Mental Traits of Sex. Chicago: Univ. 
Chicago Press, 1903. Pp. 188. 

29. Wissler, C. "The Correlation of Mental and Physical 
Tests," PsychoL Mon., 1901, 3, No. 16. Pp. 62. 

30. Woodworth, R. S. "Race Differences in Mental Traits," 
Science, N. S., 1910, 31, 171-186. 



Individual differences are quantitative rather than qual- 
itative. Popular opinion frequently classifies people in 
reference to the possession or non-possession of certain 
traits. Thus one individual is said to have a talent for 
music, another for painting, a third for mathematics, a 
fourth for organizing people. Such a characterization, 
however, results from purely practical considerations. In 
order to choose music as a vocation, or even as a serious 
avocation, for example, an individual must have a certain 
minimum of musical talent; if his degree of musical abil- 
ity falls below that minimum, he is not regarded as "a 
musical person." Furthermore, if such an individual has 
more outstanding ability along some other line, he will 
be classified in respect to the latter trait and not on the 
basis of his musical aptitude. Qualitative distinctions 
of this sort are made in practice and are based on arbitrary 
or socially determined criteria and limits. Actually, how- 
ever, every individual can be described in terms of the 
same traits. 

There are no "alternative" psychological traits, in the 
sense that one trait serves as a substitute for the other* 
No traits are mutually exclusive. It might be argued, 
however, that there are certain characteristics which a 
person may either have or not have, and that in this 
respect we may speak of qualitative differences. The 
classical examples are loss of sensation, such as blindness 
or deafness. Here, it would seem, are traits characterized 


by presence or absence: a person can see or he cannot see, 
he can hear or not hear. This, too, turns out to be a purely 
conventional and practical distinction. Anyone who has 
visited an institution for the blind knows that there are 
many degrees of blindness, and that not all those classified 
as blind are totally blind. The everyday working definition 
of blindness is any degree of visual deficiency too serious 
to permit normal activity. The same is obviously true 
of deafness and any other sensory disorder. Between 
the empirically established " normal" vision or hearing 
and what is classed as blindness or deafness there is to 
be found a continuous gradation of minor deficiencies. 
It should be added that the existence of a trait in zero 
degree, as in total blindness, is not inconsistent with the 
quantitative view of individual differences. The latter 
implies only that there be intermediate degrees rather 
than simple presence or absence. 


Since individual differences have been found to be 
quantitative, we may now ask how the varying degrees 
of each trait are distributed among people. Are individu- 
als scattered uniformly over the entire range or do they 
cluster at one or more points? What are the relative fre- 
quencies with which different degrees of a trait occur? 
These questions can best be answered by an examination 
of frequency distributions and frequency graphs. 

Like all statistical devices, the frequency distribution 
is a means of summarizing and organizing quantitative 
data in order to facilitate its treatment and reveal sig- 
nificant trends. Scores on a test, or any other set of 
measures, are grouped into class-intervals, and the number 
of cases falling within each interval is tabulated. An ex- 
ample of a frequency distribution is given in Table L 


This shows the scores of 1000 college students on a simple 
learning test. The scores range from 8 to 52 and have 
been grouped into class-intervals of four points. The 
advantages of such a table over a list of 1000 individual 
scores are obvious. 

The facts brought out by a frequency distribution can 
be made more vivid if presented pictorially by means of a 
frequency graph. In Figure I are shown the data of 
Table I in graphic form. The base line or horizontal 
axis represents the scores; the vertical axis shows the 
frequency or number of cases falling within each class- 




(After Anastasi, 2, p. 34) 

























8i I 


N 1000 

interval. The graph has been plotted in two ways, both 
being about equally common. One graph is a frequency 
polygon, in which the number of individuals within each 
interval is indicated by a point, centrally located in 
respect to the class-interval; the successive points are 
then joined by straight lines. The other is obtained by 



F / \ ' Frequency Polygon 

280 f- f\ \\ Histogram 


8? 22 
Q 200 

- 180 

- 160 
| 140 
I 120 


8- 12- 16- 20- 24- 28- 32- 36- 40- 44- 48- 52- 
11 15 19 23 27 31 35 39 43 47 51 55 


(Data from Table I.) 

erecting a column or rectangle over each class-interval, 
the height of the column depending upon the number of 
cases in that interval. This type of graph is known as a 


The reader will already have noticed certain character- 
istics of the distribution presented in Table I and Fig- 
ure i. The majority of cases cluster in the center of the 
range and as the extremes are approached there is a 
gradual and continuous tapering off. The curve shows 
no gaps or breaks; no clearly separated classes can be 
discerned. The curve is also bilaterally symmetrical, 
that is, if it should be divided by a vertical line through 
the center, the two halves so obtained would be nearly 
identical. This distribution curve resembles the bell- 


shaped " normal curve/' the type most commonly found 
in the measurement of individual differences. The the- 
oretically determined 3 ideal normal curve will be found 
in Figure 2. 

The concept of the 
normal curve is an old 
one in statistics. It first 
became prominent as the 
normal probability curve. 
The probability of the Fia a> THEORETIC^NORMAL CURVE. 

occurrence of an event is 

the expected relative frequency of occurrence of the given 
event in a very large, or infinite, number of observations. 
This probability is represented by a ratio or fraction, 
the numerator of which is the expected outcome, and the 
denominator the total possible outcomes. Thus the prob- 
ability or chances that when two coins are tossed only 
heads will come up is f , or one out of four possible occur- 
rences; the probability of one head and one tail is J; 
and that of two tails, f . If the number of coins is increased, 
say to 100, so that the number of possible occurrences or 
combinations becomes very large, we can still determine 
mathematically the chances of any one combination, such 
as all heads or twenty heads and eighty tails, occurring. 
These probabilities, or expected frequencies of occurrence, 
can be plotted graphically by the same method outlined 
above for plotting scores. The curve obtained when the 
number of coins is very large will be the bell-shaped 
normal probability curve. In Figure 3 are shown the 
theoretical and obtained frequencies for 12 dice thrown 
4096 times. In each throw, the number of dice showing 
a 4, 5, or 6 spot uppermost was determined. This number 
could, of course, vary from zero to 12, the total number 
of dice thrown. The graph shows the relative frequency 


1000 r Theoretical 

_ Observed 



| 600 


I* 400 


8" 200 

01 234 56 789 10 11 12 

Number of Dice Showing a 4, 5, or 6 Spot in Each Throw 
IN 4096 THROWS OF 12 DICE. (After Yule, 21, p. 258.) 

of each combination in the total 4096 throws. It will be 
noted that there is a very close agreement between the 
theoretical and obtained curves. 

The results obtained by tossing coins or throwing dice 
are said to depend upon C chance." By this is meant that 
the outcome is determined by a large number of similar, 
equal, and independent factors. The height from which 
a coin or die is thrown, its weight and size, the twist of 
the hand employed, and many similar conditions deter- 
mine which particular face will fall uppermost. Likewise, 
a person's height, or weight, or performance on an intelli- 
gence test can be regarded as depending upon a variety 
of independent factors, each having about equal influence 
upon the result. Thus it has been suggested that the 
operation of chance is responsible for the distribution of 
human traits according to the normal frequency curve. 

The normal curve also appears in a different situation 
as the curve of error. When repeated measurements are 
made, the results will not be identical on successive occa- 
sions. These errors are present to a greater or lesser degree 
in all types of measurement. The length of a table as 
measured by a meterstick, the speed of a simple move- 


ment, or the aesthetic appeal of a work of art will not 
remain the same on repeated observations. If a very 
large number of observations of the same object or phe- 
nomenon are made, and the results found on successive 
occasions are plotted in a frequency graph, a normal 
curve will be obtained. The errors of observation or 
measurement which produce the variation are themselves 
the result of chance factors, and hence the curve of error, 
like the distribution curve, will coincide with the normal 
probability curve. 


The implications of the normal distribution curve for a 
psychology of individual differences can be realized more 
vividly by contrasting this form of distribution with 
other possible types. The distributions chosen in partic- 
ular for this comparison are those implied by certain 
common theories and beliefs in regard to individual dif- 
ferences. They are also occasionally found with actual 
test results because of the use of faulty techniques. 

A skewed distribution is one in which the peak or 
"mode" of the curve is displaced to either side of the 
center. Such a distribu- 
tion lacks the bilateral 
symmetry of the normal 
curve. In Figure 4 will 
be found an illustration ; 
of a skewed curve, with Scores 

piling up Of SCOreS at the FlG ' * A SKEWE DISTRIBUTION. 

upper end of the distribution. Such a distribution is 
implicit in the popular conception of many character 
traits. Thus the majority of people are considered "hon- 
est" and are piled up at one extreme of the scale; from 


this point, the number of cases is believed to decrease 
steadily as the opposite extreme is approached. As will 
be shown in the following section, this type of distribution 
is not ordinarily found when objective measures or tests 
of character traits are used. 

A skewed distribution may, however, be obtained with 
any test employed on a group to which it is not suited. 
If the National Intelligence Test, which is adapted to 
grades 3 to 8, were administered to a college class, the 
large majority of subjects would score very near the max- 
imum, and the number of cases would decrease rapidly 
towards the lower scores. Similarly, if one of the many 
tests constructed for use on college freshmen were given 
to elementary schoolchildren, there would be a marked 
piling of scores near the zero end of the scale, and the 
distribution would be equally asymmetrical. Obviously 
these data could not be taken to mean that intelligence 
is not normally distributed among schoolchildren or col- 
lege students. Such skewed distributions result from the 
fact that the difficulty range of the test does not extend 
far enough in the upper or lower direction. In the one 
case, all of those subjects who have more than a certain 
minimum of the ability tested will make a perfect or nearly 
perfect score, whereas if the test had included more 
difficult items, these subjects would have scattered over 
a wide range. The same holds true for zero or very low 
scores when the test is too difficult for the group. In 
choosing a test for a given group, care must be taken to 
insure that the subjects have sufficient leeway at both 
ends of the scale. The highest and lowest scores obtained 
should be a considerable distance from zero and perfect 
scores, respectively. 

Skewness may also result from the inclusion within a 
single distribution of two normally distributed groups 


which differ pronouncedly in both average and variability. 
This effect is illustrated in Figure 5. On Graph A are 

A. Two groups Plotted Separately 

B, Two Groups Combined 


given the separate distribution curves of the two groups, 
one of which has a lower average as well as a narrower 
scatter of scores than the other. Graph B shows the 
definitely skewed curve which is obtained when both 
groups are combined and plotted as one distribution. 

A type of distribution not so frequently found as the 
skewed curve but nevertheless assumed in certain common 
practices is the rectangular distribution illustrated in Fig- 
ure 6. If individual differences were distributed in this 
manner, it would mean that 
there were as many geniuses 
and idiots as mediocre people, 
as many men whose height is 
6 feet 6 inches as those whose 
height is 5 feet 8 inches. It is 
interesting to speculate on the effect which such a sit- 
uation would have on our sense of values. Our thinking is so 
permeated with the knowledge that extreme degrees of a 



trait are relatively infrequent, that it is difficult even to 
conceive of a world in which extremity did not imply rarity. 

In spite of this fact, the assumption of a rectangular 
distribution is sometimes made in the interpretation of 
percentile scores. In the percentile system of scoring, 
the subject's standing on any test is expressed in terms 
of the percentage of people in a given group whose scores 
he equals or excels. If an individual, for example, answers 
ten questions correctly on a test, and if 50% of the group 
complete ten questions or less on the same test, then 
the individual falls just midway in the group and is 
given a percentile rating of 50. When comparing indi- 
viduals who receive, let us say, percentile scores of 90, 
80, 60, and 50, we must bear in mind that the difference 
in ability between the first two cases is greater than that 
between the last two, although in both pairs the difference 
is 10 percentile points. In order to include 10% of the 
cases between the 9Oth and Both persons, we must cover 
a much longer distance on the base line of the normal 
curve than is necessary in going from the 5oth to the 
6oth percentiles. This results from the greater clustering 
of individuals near the center of the curve, and the 
relatively small number of cases at the extremes. Only 
if the distribution were rectangular would successive per- 
centile scores represent equal units of ability. This does 
not mean that percentile scores are of no value. Like 
" mental ages," they furnish a simple and vivid means 
of expressing the subject's standing on a test. Such devices 
do not, however, furnish an equal unit scale of ability. 

Lastly, special mention should be made of the multi- 
modal distribution because of the prominent part it plays 
in current "type theories." A multi-modal curve is one 
having more than one mode or peak. Instead of a single 
clustering of individuals in the center as in the normal 


curve, or at either extreme as in a skewed curve, the 
clustering occurs at several points. The peaks may be 
equally large, or there may be a major peak and one or 
more minor ones. The most popular variety seems to be 
the bi-modal curve, with two approximately equal peaks. 
All of the common schemes of classification which place 
individuals into distinct categories presuppose some form 
of multi-modal distribution. The division of men into 
the genius, the normal, and the feebleminded, the sane 
and the insane, the sociable and the unsociable, all rest 
upon a tacit assumption that "most people" can be 
classified clearly into one of these groups, with possibly 
a few intermediate doubtful cases. It is interesting to 
note that these distinctions are much less common in 
the realm of physical traits, where continuity of variation 
is more apparent to the naked eye. 

A multi-modal curve can be obtained in any trait 
through the arbitrary selection of cases. If the sampling 
tested is not chosen at random from the general popula- 
tion, but consists of individuals selected from widely 
differing levels and arbitrarily combined into a single 
group, a multi-modal distribution will result. A group 
consisting of five-year-olds and ten-year-olds, for exam- 
ple, would present a definitely bi-modal distribution in 
intelligence test scores, as well as in height, weight, and 
many other characteristics. Were the intervening age 
groups from six to nine to be included in this sampling, 
the distribution would take on the appearance of the 
normal bell-shaped curve. 

The production of a bi-modal distribution by combining 
two curves of widely separated groups is illustrated in 
Figure 7. It will be noted that the overlapping between 
the two groups is very slight. When the overlapping is 
large, as in the case of adjacent age groups, the resulting 


combined curve will be normal and uni-modal. An ex- 
ample of a bi-modal curve plotted with actual scores is 
presented in Figure 8. The two distributions which are 
combined in this curve consist of the Army Alpha scores 
obtained by two groups in the United States army. The 
lower group includes 2773 native-born white soldiers who 
had reached no higher than the fourth elementary grade 

A. Two Groups Plotted Separately 

B. Two Groups Combined 


when they left school; the upper group consists of 3954 of 
ficers who had had four years of college work. The 
combined curve exhibits the definite bi-modality which 
would be expected. 

We have seen that various types of distributions other 
than the normal curve are frequently implied in current 
popular conceptions, and are occasionally found because 
of faulty techniques or inadequate data. It now remains 
to examine some typical findings on trait distributions 
obtained under conditions relatively free from the errors 
described. A few last words of caution should, however, 
be added. In the first place, an unlimited number of 
irregularities and variations in distribution curves may 
occur through the use of small groups. Curves plotted 


with a small number of cases present an uneven, jagged 
appearance since individual exceptions loom relatively 
large. For this reason, only curves obtained on fairly 
large groups will be considered in the following section. 

A second point to bear in mind relates to the concept 
of a mathematically perfect normal curve as contrasted 

0- 10- 20- 30- 40- 50- 60- 70- 80- 90- 100-110-120-130-140-150-160-170-180-190-200. 
9 19 29 39 49 59 69 79 89 99 109 119 129 139 149 159 169 179 189 199 209 

Alpha Scores 

AND 3954 OFFICERS WITH 4 YEARS OF COLLEGE. (Data from Yerkes, 20, pp. 773, 

to the more or less rough approximations obtained with 
actual data. In several instances, especially when the 
groups were very large, the characteristics of the distribu- 
tion curves were investigated mathematically and found 
to fall within the expected limits of normality. In many 
other instances, however, where such mathematical tests 
have not been employed, or where the curve has been 
found to deviate significantly in some one respect from 


the mathematically normal curve, we still speak of "nor- 
mal distribution." In these cases, what is meant is that 
the distribution resembles the normal curve more closely 
than it does, let us say, a skewed, rectangular, or multi- 
modal curve. It exhibits the general characteristics of 
clustering near the center with a gradual and continuous 
sloping toward the extremes. For a general picture of 
the distribution of a trait, such knowledge is sufficient. 
Only when certain statistical techniques which assume a 
normal curve are to be applied to the data, is it necessary 
to stress the requirement of mathematically established 


In Figures 9 to 22 will be found examples of distribution 
curves obtained for a wide variety of traits. Only distribu- 
tions based on large samplings have been included. The 
two smallest groups, comprising 200 and 400 cases, re- 
spectively, are taken from the field of personality testing. 
In this there is little from which to choose, since unfor- 
tunately very few frequency tables for personality tests 
are available. 

An example of the distribution of a purely structural 
trait is furnished in Figure 9, which shows the height in 
inches of 6194 English-born men. It will be seen that the 
graph approximates the mathematical normal curve to a 
remarkably close degree. Figure 10 presents the fre- 
quency curve of a more functional, physiological trait, 
vital capacity. This is the total volume of air, measured 
in cubic centimeters, that can be expelled from the lungs 
after a maximal inspiration. The measurements from 
which the curve is plotted were made on 1633 male stu- 
dents at the University of Minnesota. The general 
correspondence to the normal curve is again apparent. 





i 600 


58 60 62 64 66 68 70 72 74 76 78 80 

Height in Inches 

(After Yule, 21, p. 89.) 



2 160 



1100 1700 2300 2900, 3500 4100 4700 5300 5900 6500 7100 

Vital Capacity in Cubic Centimeters 

(After Jackson, 5, p. 94.) 


The two graphs reproduced in Figures II and 12 repre- 
sent the distribution of performance on relatively simple 
sensori-motor and mental tests. Reference may also be 
made in this connection to the data reported previously 
in Table I and Figure I. All three sets of measures were 

60- 70- 80- 90- 100- 110- 120- 130- 140- 150- 160- 170- 180- 190- 200- 
69 79 89 99 109 119 129 139 149 159 169 179 189 199 209 


STUDENTS. (After Anastasi, 2, p. 32.) 

obtained on the same group of 1000 college students. 
The tests whose distributions have been reproduced in- 
clude cancellation, Pyle symbol-digit, and a nonsense- 
syllable vocabulary test. In the first, the score is the total 
number of A's in a page of pied type cancelled in one 
minute. This is generally regarded as a simple test of 
attention and perception, although speed and control of 
movement are also involved. The symbol-digit test is a 
simple learning test of the code substitution variety. 
The vocabulary test is a more difficult learning test, also 


employing a code, which in this case consists of paired 
nonsense syllables. The distributions of all three tests 

10- 20- 30- 40- 50- 60- 70- 80- 90- 100- 110- 120- 130- 140- 
19 29 39 49 59 69 79 89 99 109 119 129 139 149 


(After Anastasi, 2, p. 34.) 

fall within the expected values of the theoretical normal 
curve. 1 

Typical results obtained with intelligence tests on large 
samplings are presented in Figures 13 to 16. Figure 13 
gives the intelligence ratings on the "combined scale" 
obtained by 93,965 soldiers in the United States army 
during the World War. This group constituted a random 
sampling of the white draft, both native and foreign- 
born. The "combined scale" ratings are based on Army 
Alpha, Army Beta, Stanford-Binet, and performance scale 

1 Mathematical tests of normality were applied to these curves (cf. Ana- 
stasi, 2). 

4 6 





i 7 



- 5 

5 10 15 

Combined Scale Scores 

(N = 93,965). (Data from Yerkes, 20, p. 654.) 



w OK 
</> ^0 


"a 20 




I 10 

56- 66- 76- 86- 96- 106- 116- 126- 136- 
65 75 85 95 105 115 125 135 145 

Standford-Binet I.Q, 

(After Terman, 14, p. 66.) 


examinations, the scores on all tests having been reduced 
to comparable terms and expressed on a single scale 
ranging from o to 25 points. Since all the recruits were 
unable to take the same test, it was necessary to combine 
scores in this manner. 

In Figure 14 will be found the distribution of Stanford- 
Binet I.Q.'s of 905 unselected schoolchildren, ranging in 
age from 5 to 14. The percentages of children whose 
I.Q.'s fell within each class-interval are given below the 
graph. Figure 15 shows the percentage distribution of 
scores made by 5952 sixth- 
grade schoolchildren on 
the Otis Advanced Exam- 
ination. This is a widely 
used group test of general 
intelligence. Finally, in 
Figure 16 can be seen a 
composite curve for college 
freshmen, obtained by ^ 



eleven different intelli- 

gence examinations ad- 

ministered to groups of 623 to 5495 freshmen in various 

American colleges. The theoretical normal curve is shown 

in broken line on the same graph. 

In the measurement of personality and character traits, 
testing techniques are still in a relatively crude and un- 
developed stage. Many sources of error remain, so that one 
should scarcely expect to find perfect specimens of the nor- 
mal distribution curve. Despite a more jagged appearance 
and many minor irregularities, however, the available 
distribution curves exhibit quite generally the fundamen- 
tal characteristics of the normal curve. Inspection of 
Figures 17 to 22 will make this apparent. 


THEORETICAL NORMAL CURVE. (After Thorndike, 15, p. 545.) 

-41- -36- -31- -26- -21- -16- -11- -6- -1- 0- +5- +10- +15- +20- 
-45 -40 -35 -30 -25 -20 -15 -10 -5 +4 +9 +14 +19 +24 

Extroversion - Scores *~ Introversion 

200 COLLEGE STUDENTS. (Data from Heidbreder, 9, p, 124.) 








1 50 





+55- +45- +35- +25- +15- +5- -5- -15- -25- -35- -45- 
+46 +36 +26 +16 +6 -4 -14 -24 -34 -44 -55 


ASCENDANCE-SUBMISSION TEST. (After Allport, i, p. 129.) 

Figure 17 gives the distribution of total introversion- 
extroversion scores on a self-rating questionnaire admin- 
istered to 200 college 
students. The posi- 
tive scores correspond 
to the introvert end 
of the scale, the nega- 
tive scores to the ex- 
trovert end. It will be 
readily seen that in- 
dividuals do not clus- 
ter at opposite ends 
of the scale, as a clear- 
cut division into in- 
troverts and extro- 





\ 150 



.1 .2 

.8 .9 .10 

3 .4 .5 .6 .7 
Cheating Ratio 


^ ij ^u, TIOS" OF 2443 SCHOOLCHILDREN. (Data from 

VertS WOUld imply. Hartshorne Ind May, 6, p. 220.) 

The greatest cluster- 
ing occurs in the center, with a gradual dropping off as the 
extremes are approached. Figure 18, giving the distribution 


of 400 male college students on a test of ascendance- 
submission, exhibits the same general form. 

Figures 19 to 22 are plotted with data taken from the 
studies of May and Hartshorne (6, 7, 8) on the measure- 
ment of character in schoolchildren. Figure 19 gives the 
distribution of "cheating ratios 5 ' for 2443 children. The 
no cheating ratio indi- 

A cates the number 

100 " / \ r 11-11 

/ \ ot times each child 

90 - / \ 

cheated relative to 
the number of op- 


! 70 

JS 50 




portunities offered. 
The obtained curve 
does not admit of 
a clear-cut division 
into "honest" and 
"dishonest," or 
those who cheat 

44. 16- 46- 76.106-136-166-196-226-256.286-316. d ^ O8e Wh d 
15 45 75 105 135 165 195 225 255 285 315 345 not. A slight skew- 

FIG. 20. DISTRIBUTION OF e p E RsiSTENCE SCORES n ^ SS 1S ex ^lblted, 
AMONG 656 SCHOOLCHILDREN. (Unpubl. data from with a tendency for 
investigation of Hartshorne, May, and Mailer, 7.) , -, 

" scores to pile up at 

the "honest" .end, but this may be caused by a limitation in 
the scale. The tests probably presented an insufficient num- 
ber of situations in which cheating was made very easy or 
involved a relatively minor "moral issue." This would cut 
the scale short at the lower end and produce an excess of zero 
or very low cheating scores. The distribution of combined 
scores on several tests of service or cooperativeness, pre- 
sented in Figure 20, exhibits a very close resemblance to 
the normal curve. The same general features also char- 
acterize the distributions in Figures 21 and 22. The 
former gives the combined scores on several persistence 


60- 65- 70- 75- 80- 85- 90- 95- 100-105- 110-115- 120- 125- 130-135- 140- 145-150- 155-160- 
64 69 74 79 84 89 94 99 104 109 114 119 124 129 134 139 144 149 154 159 164 


(UnpubL data from investigation of Hartshorne, May, and Mailer, 7.) 

tests; the latter is based on the results of a question- 
naire of moral knowledge, designed to measure "good 


One is tempted to compare the distributions of different 
traits in the effort to discover the relative variability of 
such traits. Do individuals differ more in physical or in 
mental traits? Are they more alike in intellectual or in 
emotional characteristics ? These and many similar ques- 
tions have been raised repeatedly and answers have oc- 
casionally been offered. 1 It is probably correct to state 

l Cf., for example, the interesting although rather futile discussion by Wech- 
sler (19). 


as a general principle that individual differences will be 
larger in the more complex than in the simpler traits. 
Any characteristic which depends upon the simultaneous 
variation of a large number of factors will exhibit more 






$ 80 

S 7 

j 60 





i a \ i i \ till 



10- 15- 20- 25- 30- 35- 40- 45- 50- 55- 60- 65- 70- 75- 80- 
14 19 24 29 34 39 44 49 54 59 64 69 74 79 84 


(Unpubl. data from Hartshorne, May, and Shuttleworth, 8.) 

marked differences than one which is determined by rela- 
tively few factors. An illustration from coin tossing will 
again prove serviceable. If two coins are employed, the 
number of possible combinations which may result is 
only four; if, however, the number of coins is increased 
to ten, the possible variations, or patterns of head-and- 
tail combinations, total 1024. A complex trait is one 
which is determined by a large number of factors or con- 
ditions, and hence it will be expected to exhibit a greater 
range of variation. 


Apart from this rather obvious generalization, little can 
be said about the extent of individual variation in differ- 
ent traits. Upon close analysis, in fact, the question of the 
extent of variability itself appears to be ambiguous and 
quite meaningless. The first problem which confronts 
one when trying to compare human variability in sep- 
arate traits is that of the measuring rod employed for the 
different traits, or the units in which the measurements 
are reported. That the particular scale employed affects 
the amount of variability found is easily demonstrated. 
If the height of buildings in one city is measured in feet 
and in another city in yards, the buildings in the former 
city will seem to vary among themselves three times as 
much as in the latter, even though the actual range in 
height may be identical in the two cities. Fortunately, 
feet can be translated into yards and vice versa. But 
this cannot be done with the units of psychological tests. 
The number of problems correctly solved on an arithmetic 
test cannot be transmuted into the same kind of units as 
neurotic symptoms checked on an emotional adjustment 
questionnaire. The only, solution offered for this difficulty 
is the use of measures of relative variability. 

All indices of relative varUbility.^ig^raiiS 8 * O ne such 
measure, the coeffici^^^oj^variation^ is JOUE^^ 
the standard deviation 1 by the ayej;a^ r g|lth^^ 
Tims variability is expressed in relation to the average, 
the difference in units from one test to the other being 
automatically ruled out. For the same purpose, thojj-lia 
between the highest and lowest scores or the tenthJhigiLjest 
t and tenth lowest, or, any, other similar^coi^^ 

1 The standard deviation is a statistical measure of the extent of variability 
within a group. It is found by subtracting each score from the average, squaring 
the differences, and then finding the square root "of the average of these squares. 


frequently cpmputed. Although in current use, all such 
measures are open to a serious objection. The difficulty 
arises from the fact that psychological scales do not 
measure the individual from a true zero of ability as a 
base. Thus a zero score on Army Alpha does not mean 
zero intelligence, as was demonstrated when soldiers who 
had failed to make any score on the Alpha were given the 
Beta or the Stanford-Binet examinations. The Army 
Alpha begins at an arbitrary level of ability which is 
higher than that reached by some individuals; anyone 
falling below that level will receive a zero score. 

The custom of measuring from "absolute zero" in our 
physical scales is so general that it is difficult to conceive 
of the effects of using a scale that begins at an arbitrary 
zero point. Think of a measuring stick on which height 
is measured, not from absolute zero or no height at all, 
but from some arbitrary point such as two feet. The fol- 
lowing diagram illustrates the situation. Any object 


4 -FOOT BOY 6-Foi)T MAN 

two feet or less in height would register zero on this scale. 
If such a scale were to be employed only to measure the 
heights of individuals over five years of age, the arbitrary 
limit would perhaps not appear so absurd, since no one 
would be under two feet tall. This is in fact what has 
occurred in the construction of psychological tests. Since 
the Army Alpha, for example, was designed for adult 
men, it would have been wasteful and, from a practical 
standpoint impossible, to extend it down to the intel- 
lectual level of a newborn child. To return to our yard- 
stick with an arbitrary zero point at two feet, let us 
suppose that it has been used to measure the heights of a 
six-foot man and a four-foot boy. The man will measure 


four feet and the boy two feet, as has been indicated on 
the diagram. For many purposes, no error has been 
introduced in the data by the use of the artificial zero 
point. On any scale, the man is two feet taller than the 
boy. If, however, we express their respective heights as a 
ratio, we reach the conclusion that the man is twice as 
tall as the boy (-f). This is not true of their actual heights 
from absolute zero, the man being only i| times as tall 
as the boy (f). The subtraction of a constant, two feet, 
from both heights has yielded a false ratio. 

Such is the effect of aa .arbitrary zero point on any 
value which involves the division of one measure by an- 
other. For this reason, ratio or other relative measures 
cannot be employed with the large majority of psycho- 
logical tests which are not scaled from absolute zero. 1 
Such measures would hold true only for the specific tests 
in the form in which they were employed; the addition 
or removal of a few easy items at the lower end of the 
scale would completely alter the relative variabilities. 
Obviously the values thus computed could not be regarded 
as very meaningful. We arrive at the collusion, then,, 
that with available psychological tests it is imposjible^to 
compare variability from one trait to another. 

Other difficulties also appear as the problem is inspected 
more closely. I^gjthe^ 

it^refer^ to the whole human race? Which individuals, 
if any, shall be omitted m' order to arrive at an estimate 
of human variability? Shall those who are regarded as 
definitely pathological and represent very extreme devia- 
tions be excluded? If so, where should the line be drawn 
between a typical human group and an abnormal deviant? 

1 The only important exception to date is the CAVD Intelligence Examina- 
tion, prepared by the Institute of Educational Research at Teachers' College, 
Columbia University (cf. Thorndike, 15). 


It seems reasonable, for example, to exclude from an 
estimate of the range of human variation in speed of 
movement one who has suffered an injury which renders 
his movements slow and halting. It is but a short step 
from this procedure to that which would exclude those 
incapacitated through disease. How, then, would this 
criterion operate in the case of a feebleminded person 
in whom no physical defect can be discovered ? How far 
shall; this process of eliminating extreme cases be carried? 

A further question relates to the factors which are to be 
held constant in measuring the variability of any one 
trait. How homogeneous should the group be? The 
inclusion of children of different age levels would cer- 
tainly, increase the extent of variation in most traits. If 
only the range of individual differences within a fairly 
homogeneous population is desired, the difficulty of de- 
fining the required degree of homogeneity is encountered. 
Many traits are influenced by the social and economic 
level in which the individual finds himself. Should condi- 
tions of this sort also be held constant? Should differences 
in/; speed, of performance be ruled out when determining 
variability in "intelligence"? Such questions could be 
raised ad inftnitum. unless an arbitrary limit is set up and 
adhered to consistently for the purposes of some one 
particular investigation. 

We may conclude from this analysis that the question . 
of, the extent of individual 'differences in different traits 
cannot be answered unless put in very specific terms. 
The population must be defined in detail within each 
investigation and the nature of the trait measured must 
be made clear, especially by indicating which conditions 
are to be held constant and which will be allowed to vary. 
Obviously all conditions whjiih affect a given trait cannot 
be held constant; otherwise variation would disappear. 


It should be added that at the -present stage in the .de- 
velopment of mental testing, owing to the use of incom- 
parable;, units and arbitrary zero points, the question 
cannot be answered at all, in any form. 


Individual differences ,are not to be regarded as '.char- 
acteristically human. Variation is a universal phenomenon 
throughout the organic scale. "All cats look grey at 
night/' but upon closer inspection each becomes an indi- 
vidual in his own right. Cursory or inadequate observa*- 
tion often creates an impression of similarity : brrey,eh 
identity among members of a group while the differences 
pass unnoticed. For this reason, only the very exceptional 
deviations among animals have attracted attention in the 
past, all other members of the species having been im- 
plicitly relegated to the limbo of "normality." 

Several cases of exceptionally "gifted" animals <x have 
been described by their trainers or by observers, the 
remarkable feats of the animals having aroused the wonder 
"and admiration of spectators. Among the most famous 
examples is Clever Hans, a stallion purchased in 1900 
by a Mr. Van Osten of Berlin and subsequently trained 
by him. The horse was first taught a conventional alphas- 
bet in which each letter was represented by :a fcertain 
combination of taps with the forefoot.- Digits -were; iiiflir 
cated by the appropriate number of taps; By this sys,tein| 
the horse learned to "count "--objects presented * to ";Mni 
and also to perform all forms of -simple arithmetic opasa^- 
lions: "He. .could handle fractions, first changing: them 
into decimals; "He was able to give the correct answer 
to such a problem as the following: "I "have a number in 
: mind; 1 subtract 9 and have 3 as a remainder; what 1 is 

i For a fuller discussion sfee Watson (18, Ch. IX) and Tinklepaugh (16). 


the number?" He seemed to read German readily, and 
if presented with a series of cards containing written 
words, he would step up and point with his nose to any 
words required of him. He answered simple questions 
put to him orally, tapping out each letter of the answer 
in his conventional alphabet. He could give the date of 
any day one might mention, would tell time to the min- 
ute, and was able to analyze a discordant clang, telling 
his observers which note should be changed. 

Most of these feats are not, to be sure, as remarkable 
as they appear at first glance. Thus, it was found that 
Clever Hans was unable to respond correctly to a prob- 
lem if no one present knew the answer. Likewise, when 
the observers were concealed, the horse failed. The un- 
usual achievements of Clever Hans and of many other 
performing animals result not from an understanding 
of arithmetic or an ability to read but from an exception- 
ally keen observation of slight cues given by the observers. 
The trainer, or other persons present, will make some 
slight gesture, such as lifting the head a few millimeters, 
as soon as the animal has tapped the correct number of 
times. Such cues, it may be added, are usually given un- 
intentionally and unconsciously. They may be too slight 
to attract the attention of spectators, but an observant 
animal will learn to respond to them. Although destroy- 
ing some of the glamor which such feats have had for the 
public, this explanation does not imply that the task of 
learning to observe and respond to the proper cues is an 
easy one which any animal could accomplish. 

There remain, furthermore, the cases of animals who 
have been shown genuinely to respond to a wide variety 
of verbal commands in the absence of any other cues, or 
who have learned intricate combinations of movements, 
or have in many other ways proved their ability to react 


to very complex situations. Performing dogs, such as 
"Fellow" who could respond to approximately 400 words 
and execute the same commands even when worded dif- 
ferently, have been repeatedly exhibited. Dogs who lead 
the blind show a remarkably keen adjustment of their 
responses to the changing demands of the situation. Chim- 
panzees have been taught a wide variety of acts such as 
skating, riding a bicycle, eating with knife and fork, 
unlocking doors. The performances of circus animals, 
and especially "musical" sea lions, are well known. The 
observation of such animals, even when stripped of pop- 
ular overstatement, still yields instances of marked indi- 
vidual differences. 

Nor is the evidence for individual variation among 
infrahuman animals confined to the study of unusual 
cases. Every laboratory investigation employing more 
than one subject has revealed individual differences. 1 
Animal psychologists have not as a rule been concerned 
with the measurement of variability, so that the data on 
this problem are usually mentioned only incidentally and 
frequently are not given in quantitative form. Whenever 
such data are reported, however, the range of perform- 
ance in a randomly selected group is surprisingly large. 
Wide individual variation has been found in every phase 
of behavior investigated, such as the amount of general 
spontaneous activity, the relative strength of motives, 
speed of movement, quickness of learning simple tasks, 
and behavior in more complex problem-solving situations. 
Some typical quantitative results on learning behavior 
have been brought together in Table II. The average, 
range, and standard deviation for each set of data have 
been given whenever available. 

1 Cf., for example, the discussion of this problem from various angles by 
Tryon (17). 


; first set of data are taken from experiments on 
conditioning. Two stimuli, -such as a flash of light and an 
electric shock to the foot, are presented together. After 
a number of combined repetitions of these stimuli, the 
withdrawal response becomes conditioned to the light, 
i.e-j the animal will withdraw its foot upon appearance 
of the light alone, without the presence of the electric 
shock. It is customary in such an experiment to refer 
to the original stimulus (in this case, the shock) as the 
conditioning stimulus, and to the other as the condi- 
tioned stimulus. The general nature of the condition- 
ing and conditioned stimuli employed in each experi- 
ment has been indicated in Table II, together with the 
type and number of animals investigated. It will be 
noted that the number of combined repetitions of the 
two stimuli required to establish the conditioned reaction 
differs widely from individual to individual within each 

The- second set of data are taken from a series of learning 
projects conducted at the Columbia University laboratory 
of comparative psychology. Small samplings of guinea 
pigs, albino rats, common short-haired cats, and monkeys 
of.twb species Were tested with the same type of " problem 
box 7 ' in which a series of steps of - increasing complexity 
is> presented to the animal. The box consists essentially 
of an outer and an inner cage, the latter containing the 
incentive which the animal obtains at the completion of 
each successful trial. In the outer cage are three plates 
to be depressed in a given order by the animal before the 
door to the incentive compartment is opened. In Table !!> 
only' the number of trials required to learn step I ,are 
reproduced, since this is the only step learned by all>of 
the groups. The problem in step I consists simply in 
stepping on the first plate to the right as the animal en- 






Combinations for Condi- 


No. of 





Range 1 












Light - 



























1 Organism 

No. of 

Step I 

Trials to Learn Step I 

Range in 























46.69 J 






















Type of Maze 

No. of 

/""./T .. -,_ 

No. of Trials to, Learn 


Range " 

? s.p. 

Albino rats 

8 cul-de-sac ele- 

;' / 

1 i : i 

vated skeleton 

-V*; ., <; 


1 86 



Albino, rats 

Equal-unit maze 




* From Razran (13), pp. 308-309. 
t From Fjeld (4), p. 528, and Koch (11), pp. 186, 208. 
J Cf. footnote on p. 62. 

From Corey (3), p. 256, and Jackson (10), p. 27. 



ters. 1 The other steps involved stepping on plates I and 2; 
I, 2, and 3; I, 2, 3, and back to 2; I, 2, 3, 2, i; and so 
on to other combinations. Although these studies were 
conducted mainly to determine the highest number of 
steps which any animal within a given species could 
master, the data yield striking evidence of individual 
differences within each species. Not only the number of 
trials required to learn each step, but also the number 
of steps which could be learned, differed from individual 
to individual. Thus in the group of guinea pigs, some 
were unable to learn even step I, while others succeeded; 
among the rats, some learned two steps, some one, and a 
few none; among the cats, the range is from 3 to 7 steps; 
among the rhesus monkeys 2 to 22, and among the cebus 
5* to 15. Thus the individual variation was so large that 
an individual could easily be found in a "higher" species 
who was unable to learn as much as a given individual 
in a "lower" species. 

In the third section of Table II are presented some typ- 
ical data on maze learning among albino rats. The 
individual differences are again marked, as is indicated 
by the standard deviations of the number of trials re- 
quired to master the correct path in each maze. Thus it is 
apparent that close observation and measurement of ani- 
mal behavior reveal fully as wide an individual variation 
as the studies on human subjects. 

An interesting example of the normal distribution curve 
in a functional trait in animals is to be found in the photo- 
graph and accompanying curve reproduced in Figure 23, 
The photograph shows horses on the race track just 
before the finish. The relative position of the horses 

1 In the study on cats, the problem set in step I was simpler, the animal being 
allowed to step on any one of the three plates. The data on this group are there- 
fore not directly comparable to those on the other species. 


,9608 .9650 .9686 .9753 .9811 .9847 .9875 .9903 .9922 

Quality of Performance or Racing Capacity Shown 

EPSOM DOWNS, JUNE 5, 1929. (After Laughlin, 12, p. 215.) 

furnishes a vivid demonstration of the normal distribution 
of racing performance. A few are in the lead, an equally 
small number lag behind, and the majority are scattered 
in intermediate positions. The graph is a frequency curve 
of the "racing capacity" of the same horses, computed 
by a standardized formula. 



1. Allport, G. W. "A Test for Ascendance-Submission," 
/. Abn. and Soc. PsychoL, 1928-29, 23, 118-136. 

2. Anastasi, A. "Practice and Variability," PsychoL Mon., 
i934 ? 45. No. 5. Pp. 55. 

3. Corey, S. M. "An Experimental Study of Retention in the 
White Rat," /. Exp. PsychoL, 1931, 14, 252-259. 

4. Fjeld, H. A. "The Limits of Learning Ability in Rhesus 
Monkeys," Genet. PsychoL Mon., 1934, 15, 369-537. 

5. Harris, J. A., Jackson, C. M., Paterson, D. G., and Scam- 
mon-, R< L. The Measurement of Man. Minneapolis : Univ. 
Minn. Press, i3o. Pp. 215. 

6. Hartshorne, H., and May, M* A. Studies in Deceit. N. Y.: 
Macmillan, '1928. Pp. 306. 

7. Hartshorne, H., May, M. A., and Mailer, J. B. Studies in 
Service and Self-Control. N. Y.: Macmillan, 1929. Pp. 559. 

8. Hartshorne, H., May, M. A., and Shuttleworth, F. K. 
Studies in the Organization of Character. N. Y. : Macmillan, 
1930. Pp. 503. 

9. Heidbreder, E. "Measuring Introversion and Extrover- 
sion," J. Abn. and Soc. PsychoL, 1926, 21, 120-134. 

10. Jackson, T. A. "General Factors in Transfer of Training in 
the White Rat," Genet. PsychoL Mon., 1932, n, 1-52. 

11. Koch, A. M. "The Limits of Learning Ability in Cebus 
Monkeys," Genet. PsychoL Mon., 1935, I 7? I ^S~~ ::i 34- 

12. Laughlm, H. H. "Racing Capacity In the Thoroughbred 
Horse," Sci. Monthly, 1934, 38, 210-222; 310-321. 

13. Razran, G. H. S. "Conditioned Responses in Animals 
Other than Dogs," PsychoL Bull., 1933, 30, 261-324. 

14. Terman, L. M. The Measurement of Intelligence. N. Y.: 
Houghton Mifflin, 1916. Pp. 362. 

15. Thorndike, E. L., Bregman, E. 0., Cobb, M. V., and Wood- 
yard, Ella. The Measurement of Intelligence. N. Y.: Teach- 
ers College, Columbia Univ., Bur. Pub., 1926. Pp. 616. 

16. Tinklepaugh, O. L. "'Gifted' Animals." Ch. XV in Com- 


parative Psychology , ed. by Moss, F. A. N. Y. : Prentice- 
Hall, 1934. Pp. 529. 

17. Tryon, R. C. "Individual Differences." Ch. XIII in Compar- 
ative Psychology , ed. by Moss, F, A. N. Y. : Prentice-Hall, 
1934. Pp. 529. 

1 8. Watson, J. B. Behavior: an Introduction to Comparative 
Psychology. N. Y.: Holt, 1923. Pp. 439. 

19. Wechsler ? David. The Range of Human Capacities. Balti- 
more: Williams and Wilkins, 1935. Pp. 159. 

20. Yerkes, R. M., ed. "Psychological Examining in the United 
States Army," Memoirs Nat. Acad. Sri., 1921, 15. Pp. 890. 

21. Yule, G. U. An Introduction to the Theory of Statistics, 
London: Griffin, 1919. Pp. 422. 


Why do individuals differ from one another? What 
are the factors which produce variation? These questions 
have stimulated intense discussion and led to lively con- 
troversy. In addition to its fundamental theoretical im- 
port, the problem of the causation of individual differ- 
ences has far-reaching practical significance in many fields. 
Any procedure involving the control of human develop- 
ment must be based upon an understanding of the factors 
which influence such development. All educational meth- 
ods make some assumption regarding the causes of indi- 
vidual differences. Is the main function of education to 
produce certain desirable traits, or merely to offer oppor- 
tunities for the development of the child's potentialities? 
Volumes have been devoted to argumentative and fre- 
quently verbose analyses of this question. The empirical 
accumulation of facts on the causes of individual variation 
alone can furnish a conclusive answer. The type of edu- 
cational activities, vocations, and other pursuits tradi- 
tionally allotted to men and women rests upon certain 
beliefs regarding the cause of sex differences in psycho- 
logical traits. Relationships among racial and national 
groups, and the attitudes of one group towards another, 
are built up on the basis of theories, either implicitly 
assumed or overtly stated, regarding the origin of racial 
and national characteristics. Any caste system implies 
an hereditary differentiation of people. Such systems, 
although not formally prescribed, are quite prevalent 
and operate in the choice of a vocation and 'similar 



situations of everyday life. The interpretation of family 
resemblances, and even in some cases the development 
of family groupings themselves, rest upon specific under- 
lying hypotheses regarding the causal factors in human 
resemblance and dissimilarity. 


The causes, of individual variation are to be sought in 
the individual's hereditary background and in the en- 
vironmental conditions to which he has been exposed. 
Every trait or behavior manifestation of the individual 
depends both on his heredity and on his environment. 
Traits and activities cannot be classified into those which 
are inherited and those which are acquired. The.pcp&lem 
thus resolves itself into a determination of the relative 
contribution of hereditary and environmental factors in 
the development of the individual. To what extent can 
the development of any given characteristic be altered 
by the control of environmental influences, and to what 
extent is such modification limited by hereditary condi- 
tions? Individual variations found under similar heredi- 
tary conditions may be attributed to the operation of 
different environmental factors. Similarly, when the en- 
vironments are sufficiently similar, any dissimilarity of 
behavior may be regarded as indicative of a difference in 
heredity. We may speak, therefore, of hereditary and 
environmental determiners or factors in the development 
of a given characteristic, although such a dichotomy 
cannot be applied to traits. 

How does heredity operate in the development of the 
individual? The understanding of the mechanism of 
heredity has been greatly furthered by the concept of the 
gene. The individual begins life at conception with the 
union of one germ cell from each parent, the ovum of the 


female and the spermatozoon of the male. Each of these 
cells contains hundreds of thousands of very minute parti- 
cles, called genes. A gene is the carrier of a "unit char- 
acter," i.e., an hereditary factor or influence which always 
operates as a unit, or in an all-or-none fashion. These 
unit characters of the geneticists are not to be confused 
with traits as ordinarily conceived, but are of a much 
more elementary nature. Thus, even a relatively simple 
characteristic such as eye color depends upon the com- 
bined influence of a very large number of separate genes. 
Such complex hereditary determination would of course 
produce varying degrees of a trait, even though the 
individual genes may be characterized only by presence 
or absence. 

It is obvious that any attempt to identify psychological 
characteristics, and especially such a manifold and ill- 
defined phenomenon as "intelligence/ 5 with unit chaty 
acters is entirely inconsistent with the concepts and data 
of genetics. Nevertheless such an attempt was actually- 
made in the zeal which followed the early spread of menta} 
tests. 1 The experimental location of the specific genes 
which contribute towards the development of observable 
traits of the organism is, on the other hand, an extremely 
difficult task. In recent years rapid strides have been 
made along these lines by geneticists, as is illustrated by 
the excellent work of Morgan (18) on the gene "maps" 
of the fruit fly, Drosophila melanogaster. This phase of 
the geneticist's work is, however, still in its infancy. 
The data available at present are too meagre to be of 
any di'rect assistance in the understanding of complex 
behavior phenomena. 
f The^ere^ 
found in the" almost unlimited variety of possible #ene 

, , - ', , , , . ' ' f <* fr* ,* n ... ,-^*'< <f "<- *., n > f^tmf 

' ' l Cf. Goddard (8), especially Chs, VII and VIIL 


combinations which presents itself, especially in the case 
of such a complex organism as man. When male and 
female germ cells unite at conception, the fertilized ovum 
contains two sets of genes, one from each parent. These 
genes combine in a variety of ways in each of the daughter 
cells, and hence the different germ cells of the resulting 
organism will not be identical in their gene constitution. 
The individual offspring of this organism will therefore 
differ among themselves because they have developed 
from different germ cells. When we add to this the fact 
that such offspring result from the union of germ cells 
from two parents, each of whom has , germ cells which 
differ among themselves, the number of possible varia- 
tions becomes very large. Thus- it is small wonder that 
duplicate individuals are not produced by chance. 

TJie. only exception to this individual diversity of "gene 
constitution is that of identical twins, which develop from 
a^ single fertilized ovum. Such twins are always of the 
same sex and identical in appearance. Fraternal twins, 
on the other hand, do not reveal such close resemblance 
and may be either of the same or opposite sex. The heredi- 
tary similarity of fraternal twins is no greater than that 
of ordinary siblings, 1 since they result from the simul- 
taneous development of two different cells. Fraternal 
twins are, however, exposed to the same prenatal en- 
vironment, which may be an important factor in render- 
ing them similar in their subsequent development. 

Certain popular misconceptions regarding the mani- 
festations of heredity should be cleared up at the outset. 
In the first place, there is a ,c,pmmon belief thatjnj^^tjance 

...".....,. v^,,^*-***"***"^ ****" < * "" "* "' "' ,..' ^f^f'.-M'ti"' mmm ^ _ 

is indicated only by resembla^ 

ancestors. This is shown to be false by a consideration 

of the mechanism of inheritance. The germ plasm is 

1 Siblings is a general term employed to cover both brothers and sisters. 


continuous from generation to generation and is not "pro- 
duced" by the individual parents. The parents simply 
transmit this germ plasm to the offspring. Hence the indi- 
vidual inherits from all of his direct ancestors, and not 
only from his parents. Some characteristic which may 
have been latent for many generations may become domi- 
nant because of a particular combination of genes and 
the result will be an individual very unlike his parents 
or immediate forbears in some one respect. Instances of 
this sort are not uncommon in family histories. In such 
a case, heredity actually serves to make the child unlike 
hisi, parents. 

A further possible source of misunderstanding is to be 
found in the common, habit of speaking about functions 
and activities as determined by hereditary factors. ^Hered- 
ity can only exert a direct control over the development 
of structures. Insofar as a given activity involves the 
presence of certain structures, such as vocal organs, hands, 
glands, nervous system, the hereditary factors underlying 
the development of these structures will influence activity. 
Likewise, the nature and degree of development of organs 
will affect their functions. But this is only a limiting con- 
dition imposed upon the development of a given type of 
behavior. Htei^dijtl!;,rjactors may prevent the appearance 
of a function through the aBsence of the necessary struc- 
tures, but the converse does not hold. The presence of 
such structures does not imply that the particular form of 
behavior in question will appear. 

Another popular notion occasionally met is that what- 
ever is present at birth is inherited and whatever appears 
subsequently is acquired. As it stands, this statement is 
inconsistent with the fundamental concept of development 
as an interaction of hereditary and environmental influ- 
ences, Even if reworded to eliminate this inconsistency, 


however, it is still misleading. Thus it is equally false 
to think of the operation of hereditary influences in the 
development of any trait as ceasing at birth or, conversely, 
to think of environmental influences as beginning to oper- 
ate at birth. Hereditary factors may influence the de- 
velopment of the individual long after birth, and in fact 
throughout the life span. Even the onset of death itself 
may be determined partly by hereditary factors, as sug- 
gested by the observation that longevity or "long life" 
tends to run in families. Hereditary influences may be- 
come manifest for the first time at any age. Similarly, 
environmental influences begin to operate upon the indi- 
vidual from the moment of conception. The importance 
of temperature, chemical, and other types of stimulation 
in the prenatal surroundings of the developing embryo is 
rapidly coming to be recognized. Birth is not to be re- 
garded as either a beginning or an end in the life of the 
organism, but as a relatively minor occurrence in a 
developmental continuum which begins at conception and 
ends at death. 


In general it may be said that the earlier an environ- 
mental condition operates in the life of the individual, the 
more pronounced will be its effect. After an advanced 
state of growth has been reached, the organism becomes 
much less modifiable. For this reason, the stimuli to 
which the individual is exposed during the embryonic 
stage exert a pronounced and lasting influence upon its 
future development. Variations in diet and nutrMon, 
glandular_secretion, and other "conditions of the mother 

blood have a marked , ,dfet uppn^ ^f ll .^?i^^^^ l ^' 
tHe ejcabi-y^* The structural development of the individual 


is definitely influenced by such environmental factors. 
It is also possible that a certain amount of rudimentary 
learning may occur during prenatal life. The presence of 
-certain reflexes and other simple movements in young 
embryos has been definitely established. Such responses 
may early become conditioned in various ways to changes 
of temperature, pressure, and other stimuli furnished by 
the intra-uterine environment. The study of prenatal 
behavior opens interesting possibilities, although so far 
it offers only very meagre information. In the field of 
structural development, however, the data are much more 

Many instances of experimentally induced structural 
changes in lower animals have been reported from time 
to time. A very curious transformation can be produced 
in the axolotl, a large salamander (cf. 14, pp. 117, 124- 
125). Normally, this animal has prominent external gills, 
a large tail adapted for swimming, and other character- 
istics suited for life in the water. If the young axolotl 
is fed on thyroid, it loses its gills, and its body becomes 
generally altered so that it is no longer adapted to swim- 
ming. The animal then becomes a land salamander, 
known as Amblystoma, and returns to the water only 
to lay its eggs. 

In the fruit fly, a defective gene causes the animal to 
produce "reduplicated legs," i.e., certain joints of the 
legs, or entire legs, are doubled. Although the inheritance 
of this defective gene has been definitely traced, this 
characteristic will not appear under certain environmental 
conditions (12). If animals known to have the defective 
gene are kept at a sufficiently warm temperature, the 
additional leg or joint will not develop. Successive gen- 
erations bred under these conditions will have a normal 
appearance. If, however, ' any of their offspring are al- 


lowed to develop in colder temperatures, the defect will 
reappear. This furnishes^,defimte~ illustration of ~ke iact 
that even a clearly demonstrable " inherited defect" is 
actually only a tendency to develop in a given way under 
certain environmental conditions. 

Experimentally produced " monsters " furnish very strik- 
ing examples of the influence of prenatal environment 
(24, Chs. VI >and VII). In experiments on fish eggs, 
" Siamese twin" fish have been produced by artificially 
inhibiting or slowing down the rate of development at an 
early age through cold, insufficient oxygen, or the applica- 
tion of ultra-violet rays. In some cases, one twin is much 
smaller than the other and is deformed, the larger twin 
being a perfectly normal fish. Two-headed monsters 
have been produced among tadpoles and several species 
of fish by the application of various chemical or mechan- 
ical stimuli. Striking variations in the number and posi- 
tion of the eyes of minnows have likewise been induced. 
If the eggs of the minnow are allowed to develop in sea 
water to which has been added an excess of magnesium 
chloride, peculiar eye conditions will appear in a large 
majority of the embryos. Instead of the usual two eyes, 
many will develop a centrally placed "cyclopean" eye, 
so named after the one-eyed Cyclops of mythology. Others 
may show a single lateral eye, placed to the right or left 
of the head. Or the two eyes may be abnormally close 
together. Other physical or chemical agents may be 
employed to produce the same anomalies of development. 
The determining factor in the development of a particular 
abnormality seems to be the stage at which the agent is 
introduced, rather than the nature of the specific agent 
employed. The essential effect is a change in the rate of 
development, which alters the balance of growth among 
the different parts of the organism. 


Thus we cannot even speak of certain structural char- 
acteristics as being " normal" for a given species and fixed 
by hereditary constitution. If the environment in which 
the organisms develop were to undergo a change of a more 
or less permanent nature, a different set of characteristics 
would come to be considered normal. Similarities of 
development are attributable to common exposure to an 
essentially similar environment as much as to the pos- 
session of common genes. 1 


Numerous experiments have shown the possibility of 
pronounced alteration in behavior as a result of environ- 
mental differences. Animals reared in isolation from 
other members of the species or from individuals of the 
opposite sex, or in close association with a human child, 
have developed curious modifications of behavior. Activ- 
ities which are commonly assumed to be "unlearned" and 
fixed by hereditary constitution have proved susceptible 
to marked change. Universal characteristics in behayior, 
aajn structure, ,..h,aye Be^a shown 'to result as much frqm 
common^environments and similar opportunities for learn- 
ing^as from^common heredity. A few illustrations of 
experimental attempts to alter behavior traits will be 
considered. It is understood, of course, that by alteration 
is here meant simply the production of behavior different 
from that which develops in the ordinary environment. 
There is no implication that one kind of behavior is 
fundamentally any more "natural" than another. 

The songs of different birds, generally considered so 
characteristic of the species, have been found to contain 

1 A very comprehensive survey of data showing the effect of environmental 
factors upon the development of stature and weight in the human is to be found 
in Sanders (21). 


much that is learned in their specific manifestations. A 
group of newly hatched orioles were segregated from all 
older members of the species and brought up by them- 
selves (22). When the birds reached a certain age, they 
began to sing. Their song, however, was not the character- 
istic oriole song, but a new one. When other newly 
hatched orioles were reared with the group that had grown 
up in the laboratory, the young birds in turn learned the 
new song developed by the first group. 

Similarly, a sparrow reared in a nest of canaries gradu- 
ally abandoned his own chirps and began to take over 
the canary's call note (i). After about a month of as- 
sociation with the canaries, the sparrow began to imitate 
their song. Although at first very harsh and confused, 
this song eventually developed into a genuine canary-like 
performance. These and similar experiments have shown 
that although birds will develop some sort of song when 
they reach a certain stage of structural development, 
the specific nature of the song depends upon environ- 
mental factors. 

Sexual behavior has also proved to be dege^deijtjjgpn 
""^ manifestations. Some 4 form of 

occur at a definite developmental 

stage, because of the presence of glandular secretions in 
the blood and other physiological factors. Thg particular 
way in which such activity is expressed and the object 
towards which it is directed, however, will vary according 
to environmental circumstances. In an experiment" on 
male doves reared in isolation from other members of 
the species, a number of sexual "abnormalities" were 
observed (3). The birds would bow and coo to the experi- 
menter as normal birds do to members of their own 
species. They seemed to pay especial attention to the 
experimenter's hand with which they came into contact 


when fed; one bird actually went through the act of 
copulation while on the hand taking food. Female doves 
reared in isolation developed similar anomalies of be- 
havior (2). If the experimenter stroked them and preened 
the feathers of their head and neck, they exhibited char- 
acteristic courting behavior. Egg-laying was actually 
induced in many instances by this method. Experimental 
"homosexuality" was produced in a large number of 
cases when two female pigeons were reared together. 
In such cases, the animals would display the usual court- 
ing performance towards each other, egg-laying then 
following in both. 

Equally curious variations of behavior were noted in a 
young monkey separated from its mother at the age of 
three days and brought up in isolation from all members 
of the species during the first 18 months of life (5, 6). 
The development of sexual behavior in general was mark- 
,edly delayed. During the period of isolation there was a 
minimum of the sex behavior ordinarily displayed by 
monkeys at that age. At the age of 18 months, the period 
of isolation was discontinued, and the monkey was sub- 
sequently brought up with other members of the species. 
At this time, sex behavior began to appear, but in a very 
rudimentary form. Attempts at copulation were very 
crude and trial-and-error was exhibited. Sexual activity 
was shown indiscriminately towards males and females, 
as well as towards monkeys of other species, rags and 
other soft objects, and the experimenter's arm and hand. 
With continued association with other members of the 
species, -normal sexual activity eventually developed. 
Other forms of behavior, such as feeding, play-activity, 
and grooming, were also affected by the prolonged period 
of isolation. 

The recent investigation of Kellogg and Kellogg (16), 


in which a young chimpanzee was reared for a short 
period in a typically human environment, throws further 
light upon the factors affecting behavioral development. 
The chimpanzee, a female named "Gua," was isolated 
from its mother at the age of 7! months and brought up 
in the company of the investigator's own son, Donald, 
then 10 months old. The association was continued for 
a period of nine months. The chimpanzee was not treated 
as a pet, but as a child, and the two subjects were given 
as nearly as possible identical care. Gua was clothed in 
the same manner as the child, and showed no difficulty 
in keeping on shoes, stockings, and other common articles 
of clothing. She slept in a bed with the usual accessories, 
such as sheets and blankets. Excellent progress was 
made by the chimpanzee in learning to eat with a spoon 
and drink out of a glass. She was able to manipulate 
pencil and paper and produce simple scribblings. Gua 
also learned to respond to oral language, and by the 
termination of the experimental period understood over 
50 words or simple phrases, such as: "Blow the horn" 
(in the car); "Show me your nose"; "Do you want to go 
bye-bye?" "Take it out of your mouth." The degree to 
which it proved possible to "humanize" the behavior of 
this ape is indeed suggestive, especially in view of the 
fact that the period of residence in the human environment 
was of relatively short duration and did not begin at 

What would be the effect of bringing up a human child 
in isolation or in exclusive contact with lower animals? 
Several cases of children found in such situations are on 
record. The child's condition and behavior repertory at 
the time of discovery, as well as its subsequent develop- 


ment when transferred to a normal environment, furnish 
interesting material on the heredity-environment question. 
The most famous case is probably that of the Wild Boy 
of Aveyron, as it has come to be known in the psycho- 
logical literature. In September, 1799, three sportsmen 
came upon a boy of II or 12 in a French forest. The boy 
was completely naked, unkempt, scarred, unable to talk, 
and seemed to have been leading a wild, animal-like 
existence. He was seized by the men as he was climbing 
a tree to escape their pursuit, and was subsequently 
brought to civilization. He finally came under the guid- 
ance and observation of the French physician, Itard. 
The very illuminating account which Itard published on 
his own findings has immortalized the Wild Boy of Avey- 
ron. When found, the boy seems to have been deficient 
in all forms of behavioral development, including sensory, 
motor, intellectual, and emotional. This is clearly brought 
out in the following brief description (13, pp. 5-8), 

His eyes were unsteady, expressionless, wandering vaguely 
from one object to another without resting on anybody; they 
were so little experienced in other ways and so little trained 
by the sense of touch, that they never distinguished an object 
in relief from one in a picture. His organ of hearing was 
equally insensible to the loudest noises and to the most 
touching music. His voice was reduced to a state of complete 
muteness and only a uniform guttural sound escaped him. 
His sense of smell was so uncultivated that he was equally 
indifferent to the odor of perfumes and to the fetid exhala- 
tion of the dirt with which his bed was filled. Finally, the 
organ of touch was restricted to the mechanical function of 
grasping objects. Proceeding then to the state of the intel- 
lectual functions of this child, the author of the report pre- 
sented him to us as being quite incapable of attention (except 
for the objects of his needs) and consequently of all those op- 


erations of the mind which attention involves. He was des- 
titute of memory, of judgment, of aptitude for imitation, and 
was so limited in his ideas, even those relative to his immediate 
needs, that he had never yet succeeded in opening a door or 
climbing upon a chair to get the food that had been raised 
out of reach of his hand. In short, he was destitute of all 
means of communication and attached neither expression 
nor intention to his gestures or to the movements of his 
body. He passed rapidly and without any apparent motive 
from apathetic melancholy to the most immoderate peals of 
laughter. . , . His locomotion was extraordinary, literally 
heavy after he wore shoes, but always remarkable because 
of his difficulty in adjusting himself to our sober and meas- 
ured gait, and because of his constant tendency to trot and 
to gallop. He had an obstinate habit of smelling at anything 
that was given to him, even the things which we consider 
void of smell; his mastication was equally astonishing, ex- 
ecuted as it was solely by the sudden action of the incisors, 
which because of its similarity to that of certain rodents, 
was a sufficient indication that our savage, like these animals, 
most commonly lived on vegetable products. 

It is interesting to note that the sensory deficiency of 
this boy seems to have been quite specific and in many 
instances directly traceable to his mode of life. Thus 
Itard observed that "the sound of a cracking walnut or 
other favorite eatable never failed to make him turn 
around . . . nevertheless, this same organ showed itself 
insensible to the loudest noises and the explosion of fire- 
arms" (13, p. 15). Sexual development showed the same 
general undifferentiated type of response observed in the 
case of animals reared in isolation. Following the onset 
of puberty, periods of vague restlessness and discomfort 
as well as occasional fits of sadness or anger were noted, 
without, however, the development of specific, normal 
sexual activity. 


After five years of ingenious, painstaking, and method- 
ical training, Itard abandoned the task, having failed 
to bring the boy up to normal. This has led many to 
conclude that the Wild Boy of Aveyron must have been 
an imbecile from birth, who had been abandoned by his 
parents because of his mental deficiency. Such a conclu- 
sion, however, overlooks several important points. In 
the first place, marked improvements were effected by 
the training, even though a normal level was not reached. 
For example, although the boy could not learn to articu- 
late sounds, he succeeded in learning simple written lan- 
guage, so that he was finally able to reproduce written 
words from memory and to use them "to express his 
wants, to solicit the means to satisfy them and to grasp 
by the same method of expression the needs or the will 
of others 3 ' (13, p. 84). Secondly, had the boy actually 
been feebleminded, he should very probably have been 
unable to survive in the very trying circumstances of his 
primitive environment. Finally, the fact that the train- 
ing was begun so late in life may furnish an adequate 
explanation of its lack of success. The environment of 
early childhood is too important in determining subse- 
quent development. 

The more recently discovered "wolf children" of India 
(23, 15) represent a similar case. In 1921, two girls, aged 
about two to four and eight to nine, respectively, were 
found living in a cave with wolves in a sparsely settled 
region of India. They were taken into a local orphanage 
where some attempts were made to train them. It proved 
very difficult, however, to keep the girls in good health, 
particularly because they could not be induced to eat a 
normal, varied human diet, but retained the feeding 
habits they had acquired from association with carnivo- 
rous animals. The younger girl, "Amala," died in less 


than a month; the elder, "Kamala," lived for about 
eight years. As a result, most of the observations which 
have been recorded were made on the older child. 

Kamala, like her younger companion, showed a great 
preference for raw meat. Although never known to kill 
any domestic animal, she was fond of pouncing upon 
any killed animal which she found. The odor of meat 
could be detected at a great distance and a keen animal- 
like sense of smell was generally exhibited. Hearing was 
also very acute. The eyes are described as possessing a 
peculiar glare, like the eyes of dogs or cats in the dark. 
It seemed that Kamala could see much better at night 
than in the daytime, and she seldom slept after midnight. 
When dressed, she tore off her clothes. Eating and drink- 
ing were accomplished by lowering the mouth into the 
plate, like a dog. Eventually, however, she was taught 
to use her hands in eating. Locomotion originally con- 
sisted of crawling on all fours. She finally learned to 
walk erect on two legs, although she was never able to 
run in this position. She was accustomed to emit a cry 
or howl in a peculiar voice, neither animal nor human. 
With prolonged training, she was able to say about forty 
words and form simple sentences of two or three words, 
although the original howl was still repeated occasion- 

Mention should also be made of the celebrated and 
mysterious case of Kaspar Hauser (cf. 26, pp. 290-292), 
about whom so much has been written. Some accounts 
suggest that this boy was an heir to some princely house 
and was put out of the way by political enemies. He 
was apparently confined from early childhood in a dark 
cell, not large enough for him to stand upright. No 
clothing or cover was furnished except a shirt and trousers. 
When he awoke, he was accustomed to find bread and 


water, but he never saw the person who brought them 
and he had no knowledge of the existence of other living 
creatures besides himself. He was released in 1828, when 
about 17 years of age. At this time he was first discov- 
ered, wandering aimlessly about the streets of Nuremberg. 
He could not talk, but repeatedly uttered certain phrases 
meaninglessly. He is reputed to have had a remarkable 
sense of smell and a surprising ability to see in the dark. 
His walking resembled the first efforts of a child. After 
various vicissitudes, his instruction was undertaken by 
Prof. Daumer. Under the latter' s tutelage, Kaspar Hauser 
made rapid progress, and soon learned to speak. By this 
means he was able to communicate what he recalled 
of his life in the cell As in other cases of children brought 
into contact with civilization relatively late in life., his 
education never brought him quite up to normal. 

These examples illustrate the close dependence of hu- 
man^deyelopme'nFupoii the environment in which the 
subject is reared and the type of stimulation to which 
he Jsjsxpftsjpd. If a child is deprived of normal human 
contacts, his behavior" will come to resemble in many 
ways that of a low-grade idiot. Such a condition has, in 
fact, been regarded as a sort of environmental feeble- 
mindedness and has been given the name of isolation 
amentia (cf. 26, pp. 285, 290). When a child is brought 
"up in contact with animals, striking similarity to the 
behavior of those animals is exhibited, and such behavior 
proves difficult to eradicate once it has become firmly 
established. Subsequent educational efforts are inadequate 
to undo the effects of early nurture. Rousseau's dream 
of the " noble savage " whose inner nature is allowed to 
develop, free and unhampered by human interference, 
proves to be a vain chimera. The situation has been very 
aptly summarized by Stratton (25, p. 597): 


Lack of association with adults during a certain critical 
period of early childhood, it seems likely, produces in some 
or all normal children marks like those of congenital defect. 
The evidence seems against the romantic view that a civ- 
ilized community is a chief obstacle to the development of 
personality. On the contrary, the higher forms of personality 
become possible only in and through such a community. 
By our biological endowment alone, or by this as developed 
by maturing and learning in an infrahuman environment, 
we remain man-beasts. We become human only by active 
intercourse in a society of those who already have become 


The environmental variations described in the preced- 
ing sections were all of a very drastic nature. It might 
be objected that such cases tell us little about the ordi- 
nary range of individual differences observed in every- 
day life. Then, too, the examples cited above represent 
single cases; little is known about the exact antecedents 
of the children; and the observations were not in most 
cases very well controlled. It would seem difficult to 
draw conclusions from such information alone. The facts 
of human development suggested by these strange cases 
have, however, been corroborated by data gathered from 
various other sources. The comparison of children brought 
up in different social and cultural classes or occupational 
levels presents in a much milder form the same type of 
environmental dissimilarity and concomitant behavior 
variations found in the cases of "wild children." Such 
investigations have ordinarily dealt with very large groups 
and have arrived at their results by the use of standardized 

Among the most clear-cut findings on the effect of home 
environment and schooling upon intelligence as meas- 


ured by current tests are those of Gordon (10) on canal- 
boat and gypsy children in England. Gordon's report, 
niaHe in the course of his official duties as Inspector of 
Schools, is based on the Stanford-Binet I.Q.'s and educa- 
tional test scores of various groups of children whose 
schooling is deficient. The canal-boat children were ob- 
tained from two special schools maintained for such 
groups. Their only opportunity to attend school occurs 
when the canal-boats are tied up for loading or discharg- 
ing. It has been estimated that the average school 
attendance of canal-boat children is only 5% of that in 
ordinary elementary schools. The majority are only 
able to attend school about once a month for one or two 
consecutive half-days. Their home surroundings, although 
satisfactory in respect to conditions of health and cleanli- 
ness, are intellectually of a very low order. Many of 
the adults are themselves illiterate, and each family leads 
a relatively isolated existence, with a minimum of social 

The average LQ. of the entire group of 76 canal-boat 
children was 69.6. Taken at face value, this would sug- 
gest at best a borderline group, with a few distinctly 
feebleminded individuals. Gordon's analysis of the data, 
however, brings out very vividly the influence of .the 
restricted social and educational facilities. Thus the cor- 
reratfon^betweea agp, and LQ. within the entire group 
proved to be -.755. This indicates a marked and con- 
sistent tendency, for, the older children to get lower I.Q.'s 
than t&e younger. Such a finding is quite contrary to the 
data on J growth of intelligence in the usual child. The 
discrepancy can only be understood in terms of specific 
environmental influences. The intellectual environment 
of the younger canal-boat children is not as far below 
normal as that of their older brothers and sisters. The 


younger child in any home is exposed to relatively simple 
intellectual stimulation; as the child grows older, differ- 
ences in schooling and in the cultural level of the home 
become much more apparent. 

The high negative correlation with age is corroborated 
by analysis of individual scores. In 22 cases, two or more 
children from the same family were tested. With only 
one or two exceptions, there was found a consistent drop 
inT^O- from the youngest to the eldest child within each 
family. Most of the youngest children had I.Q.'s between 
90 and 100, which would place them within the normal 
group; among the eldest, on the other hand, were several 
whose I.Q.'s were low enough to make them appear dis- 
tinctly feebleminded. A further corroborative fact brought 
out by this analysis is that the mental ages of children 
within a single family tended to be very similar, even 
though their chronological ages differed. Such a mental 
age might well represent the limit of intellectual develop- 
ment which was made possible by the available educational 
opportunities and the type of home environment furnished 
within the given family. 

Gordon's report on gypsy children lends further support 
to the interpretations offered above. A t:Qtil of M 82 gypsy 
children attending four schools werq .given .the Staafprd- 
BinetV The^ school attendance of gypsy children, although 
still below normal, is better than that of canal-boat chil- 
dren. Actual records on the group investigated showed 
that the average school attendance from the age of five 
to the time of testing was only 34.9% of the total number 
of possible school days. Living conditions were in general 
quite crude and primitive. The groups led a nomadic 
existence, having a fixed home only during a few winter 
months; it was at this time that the children attended 
school, although even then attendance was irregular. The 


gypsy children, however, mixed more frequently with other 
people and had more social contacts than the canal-boat 

The average I.Q. of the entire group of 82 gypsy children 
was 74.5. A significant positive correlation of .368 was 
found between I.Q. and percentage of school attendance. 
Those children whose school attendance had been less 
regular, then, tended on the whole to have lower I.Q.'s. 
As in the case of the canal-boat children, a significant 
negative correlation was found between I.Q. and age, 
in this group the correlation being .430. Analysis of 
siblings within each family also showed a consistent de- 
crease in I.Q. with increase in age. It is significant that 
the chief exceptions to this trend occurred in those families 
in which there had been a high percentage of school 

The findings of Gordon on both groups seem to point 
quite irrevocably to factors of home environment and 
schooling in the development of intelligence as commonly 
measured. The evidence indicates in many ways that 
the condition of mental deficiency was not present at the 
outset.. These were not, as might be supposed, select 
groups, in the sense that the duller persons are by a 
gradual process attracted into the life of the gypsy cara- 
van or the canal-boat and their offspring will in turn 
tend to be duller than average. Such an interpretation 
is inconsistent with many of the facts given above. First, 
the younger children were on the whole of normal intelli- 
gence; secondly, the older the child and the longer the 
differential effects of inferior home and school conditions 
had operated, the lower the I.Q.; thirdly, a significant 
positive correlation was found between regularity of school 
attendance and I.Q.; fourthly, the gypsy children as a 
group had higher I.Q.'s and at the same time a much 


higher percentage of school attendance than the canal- 
boat children. Nor can the greater school attendance 
of the former be attributed to more intelligent and pro- 
gressive parents, since all too frequently the local author- 
ities found it necessary to force the children to attend 
school during their brief winter periods of stable residence. 
Numerous studies have appeared on the relationship of 
occupational level to intelligence. Large groups of children 
have been tested and classified according to father's oc- 
cupation. The latter has been taken as an objective, 
easily obtained, and fairly reliable index of general cul- 
tural level. All of these studies have shown consistent 
differences in the average intelligence of children in vari- 
ous broad occupational groupings. Such data are not, 
however, unambiguous. It is difficult to determine, with- 
out probing further into the particular circumstances in 
each case, which is cause and which is effect. Several 
investigators have argued, for instance, that the Tntel- 
lectual differences found today among occupational groups 
testify to a gradual hereditary differentiation which ,has 
been going on through selection. Thus the t higher, more 
intellectual positions come to be filled by the more in- 
telligent individuals. Since intellectually superior parents 
tend to have intellectually superior offspring, the children 
in the higher occupational strata will be more intelligent, 
on the whole, than those from the semi-skilled or unskilled 
labor classes. The alternative hypothesis explains the 
intellectual development of the child in terms of the 
cultural level in which he is brought up. Thus the child 
who grows up in the home of a construction laborer does 
not have the opportunities for intellectual development 
and consequently will not attain the same mental level 
as a child of equal initial capacity brought up in the home 
of an eminent scientist 01 author. With these alternative 


interpretations in view, some of the relevant evidence 
will be examined. 

In Great Britain, two extensive surveys were conducted 
with an intelligence scale of British construction. In 
one study (4), data were collected on 13,419 children 
attending elementary and secondary schools in Nor- 
thumberland. The other study (17) was conducted on 
2047 elementary schoolchildren in the Isle of Wight. In 
both studies, only children between the ages of n and 13 
were included. The children were classified into a large 
number of groups on the basis of specific paternal occupa- 
tion. More general trends are revealed, however, when 
the occupations are grouped into certain major categories, 
The average I.Q. as well as the number of children in 
each category have been reproduced below. The data 
of the two studies are here reported together (4, p. 195; 
17, p. 127). 

Northumberland Isle of Wight 

Study Study 


N Average N Average 

IN I.Q. I.Q. 

A. Professional 137 112.2 8 106.6 

B. Managers 92 no.o 21 108.7 

C. Higher commercial class 368 109.3 83 103.3 

D. Army, navy, police, postmen 129 105.5 141 99.9 

E. Shopkeeping class 748 105,0 224 100.7 

F. Engineers 571 102.9 in 100.8 

G. Foremen 256 102.7 17 103.3 
H, Building trades 717 102.0 207 99.1 
I. Metal workers, ship-builders 820 100.9 I2 3 99-3 
J. Miscellaneous industrial workers 472 100.6 201 99.1 
K. Mining and quarrymen 5968 97.6 6 97.9 
L. Agriculture, all classes 1128 97.6 277 96.7 
M. Low-grade occupations, laborers 1214 96.0 328 96.0 
N. Seamen, bargemen, boatmen, etc. 60 97.4 

The differences, though small, show a certain degree of 
consistency. This is particularly apparent if the upper 


seven categories In the list are compared with the lower 
eight. The latter are predominantly manual occupations, 
whereas the former depend primarily upon intellectual, 
clerical, or executive functions. 

In America, similar investigations have been conducted 
on children of all ages. Goodenough (9) administered 
the Kuhlman-Binet tests to 380 children between the 
ages of 18 and 54 months. Paternal occupations were 
classified into six commonly employed categories. The 
average I.Q.'s of children within each group are presented 

Occupational Group Average I.Q. 1 

I. Professional 125.0 
II. Semi-professional (accountants, drafts- 
men, etc., and managerial) *i9-7 

III. Clerical and skilled trades 113.4 

IV. Semi-skilled trades and minor clerical 108.0 
V. Slightly skilled 107.4 

VI. Unskilled labor 95.8 

Similar data on elementary and high school students 
are to be found in a study by Higgejtj^and Nash (n). 
The Haggerty Delta 2,, a common, group intelligence test, 
was administered to children in grades 3 to 8 and high 
school in rural districts and small towns of New York 
State. The authors demonstrate that the sampling thus 
obtained is quite representative of the country at large 
in respect to occupations. The number of cases and 
median and range of I.Q. found within each occupational 
group are given below (n, pp. 569-570). The data for ele- 
mentary and high school groups have been kept sepa- 

1 The LQ.'s obtained by the children on the second administration of the test 
are given here, as these were shown by Goodenough to be more significant than 
the I.Q.'s on the first trial. 



n 6688 Elementary 

Data on 143$ High School 


School Children 




Range in 


Range in 










2O I 




Business and cler- 






































1 06 


In two studies, covering both high school and all grades 
of the elementary school, Pressey (19, 20) attempted to 
show the dependence of occupational differences in in- 
telligence upon hereditary factors. The children were all 
taken from a small middle western city with a population 
of about 12,000 and no foreign element. In the earlier 
study, all children between the ages of 10 and 14 inclusive 
were given the Pressey Group Intelligence Test; the total 
number of cases obtained was 548 and ranged academically 
from the third grade through the high school. The later 
study was conducted on 337 children between the ages 
of 6 and 8 and in grades one to three. The latter group 
was examined with the Pressey Primer Scale, a non- 
verbal test. Pressey argued that since, in the first place, 
the second group consisted of much younger children 
upon whom differential home environment had had less 
chance to operate, and since secondly, the test employed 
was non-verbal, the differences in intelligence test per- 
formance between the occupational groups could be at- 
tributed chiefly to heredity. If environment had been 
theumajor cause, the occupational ..differences, in. .intelli- 
gence found in the first study on older, children -should 
either disappear entirely. or be greatly-miHimized in the 
secbmf study. The percentage of children in each group 


whose scores fell above the median for their age is reported 
below (20, p. 369; 19, p. 94). 

Percentage above Age Median (for the 

~ , n Total Group) 

Occupational Group ^ 

Older Group Younger Group 

(Ages 10-14) (Ages 6-8) 

1. Professional 85 " 79 

2. Executive 68 *6o 

3. Artisan 41 54 

4. Laborer 39 38 

The findings of these studies are typical of investiga- 
tions on occupational intelligence. The interpretations 
offered by the authors have frequently stressed heredity 
as the underlying cause of the existing differences. What 
do the data themselves suggest? A number of facts 
should be noted before this question is answered. First, 
the_u.sL<SL.of. nonverbal -tests such as, .the Kuhlman-jBIHet 
and the Pressey Primer Scale does aot in ..itself rule out 
environmental influences. Verbal tests, to be sure, are 
more directly affected by specific training than are non- 
verbal, but the latter still imply certain stimulating cir- 
cumstances of which the child in the poorer home may 
be deprived. Confidence in the use of paper and pencil, 
adaptation to adults outside the family, practice in fol- 
lowing directions, familiarity with pictures, and many 
similar conditions will influence the child's performance. 

Secondly, it is impossible tomake a,umver,sal,stateaient 
that differences,, resulting, from environmental lackers 4n~ 
crease with age, whereas those owing principally j:,Q.,.hred- 
itafy factors are manifested from a-ver^eaziy-age. This 
was found to be the case in the groups of canal-boat and 
gipsy children investigated by Gordon. It is not true, 
however, of children whose school attendance is normal, 
but who may come from inferior homes. In such a group, 


we should in fact expect intellectual inferiority to be 
present at the preschool level, when the child has been 
exposed only to the inferior home surroundings; as the 
children grow older and the influence of equal schooling 
becomes effective, the original differences may actually 
become reduced. The differences will not disappear, of 
course, because of the ineradicable nature of early influ- 
ences. In a group from a small city such as was employed 
by Pressey, for example, the schooling of all the children 
was probably very similar and hence there was no in- 
crease in intellectual differences with age among the oc- 
cupational groups. The large Amount .of overlapping of 
scores in the various groups is also to be expected from 
tEe equalizing influence of universal education. Further- 
more, occupational classes are not a sufficient index of 
general cultural level, and this too may account for 
the marked overlapping found. From every angle, then, 
the data seem to be consistent with an environmental 

No discussion of occupational intelligence is complete 
without mention of the vast array of data on this subject 
collected in the course of the army testing. These data 
have subsequently been worked over to show average 
and range of scores obtained by men in each of 96 major 
occupations (cf. 7). The differences in average score are 
large when extreme groups are compared, but the over- 
lapping of individual scores is pronounced throughout. 
The influence of specific environmental stimulation is 
again apparent. Thus the Army Alpha, being predom- 
inantly verbal in content, would be expected to place 
at an advantage those individuals who have been engaged 
in office work, even if this be of a simple nature. Such 
has actually been found to be the case. Routine clerical 
workers, for example, obtained higher average scores (96, 


91) than highly skilled mechanics (74, 66). It would seem, 
then, that investigations of occupational intelligence, 
whether conducted on adults or children, serve but to 
illustrate the dependence of intelligence upon the psy- 
chological milieu in which the individual develops. 


1. Conradi, E. "Song and Call-Notes of English Sparrows 
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2. Craig, W. "The Stimulation and Inhibition of Ovulation 
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3. . "Male Doves Reared in Isolation," /. An. Beh., 1914, 

4, 121-133. 

4. Duff, J. F., and Thomson, G. H. "The Social and Geo- 
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5. Foley, J. P., Jr. "First Year Development of a Rhesus 
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6. . "Second Year Development of a Rhesus Monkey 

(Macaca mulatto) Reared in Isolation during the First 
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Children and Parental Occupation," /. Educ. PsychoL, 
1924, 15, SS9-S72. 

12. Hoge, M. A. "The Influence of Temperature on the De- 


velopment of a Mendelian Character/' /. Exper. Zoo/., 
1915, i8, 241-285. 

13. Itard, J. M. G. The Wild Boy of Aveyron (transl. by G. and 
M. Humphrey). N, Y.: Century, 1932. Pp. 104. 

14. Jennings, H. S. The Biological Basis of Human Nature. 
N. Y.: Norton, 1930. Pp. 384. 

15. Kellogg, W. N. "A Further Note on the 'Wolf Children' 
of India," Amer. J. PsychoL, 1934, 46, 149-150. 

1 6. Kellogg, W. N., and L. A. The Ape and the Child. N. Y.: 
Whittlesey House, McGraw-Hill, 1933. Pp. 341. 

17. McDonald, H. "The Social Distribution of Intelligence in 
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1 8. Morgan, T. H., Bridges, C. B., and Sturtevant, A. H. The 
Genetics of Drosophila. Hague: Nijhoff, 1925. Pp. 262. 

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and Poor Environment upon Results with Tests of Intelli- 
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Pp. 535- 


The interpretation of family resemblances is compli- 
cated by the fact that close relatives generally live to- 
g"etEer. The environment of individuals within a single 
home is certainly more similar than in any other situation 
outside of an experimental set-up. As a result, the two 
classes of factors, hereditary and environmental, operate 
simultaneously to produce greater likeness within the 
ordinary family than is found among individuals chosen 
at random. The closer the hereditary relationship, fur- 
thermore, the greater the environmental proximity. Thus 
parents and children, and brothers and sisters usually live 
in the same home, whereas more distant relatives, such 
as uncles and nephews, or cousins, come into less frequent 
contact. Not only are related individuals exposed to 
common environmental stimulation because of similarity 
of living conditions, but they also constitute in part each 
other's environment and are rendered more alike by this 
mutual interaction. It^aa^jW^seem that family groupings 
offer an excelleirt^j^^ qFTnvlron- 

jdevelopjxient ^ 


Curiously enough, however, family resemblances are 
commonly attributed directly to the operation of heredity. 
The child is described as having his father's business 
acumen, his aunt's musical talent, "taking after" his 
grandfather in obstinacy, and perhaps inheriting a keen 
sense of humor from an Irish grandmother on his father's 
side! The successful son of an eminent family attributes 



his accomplishments to the fact that he is well-born. A 
lecturer's vigor and zeal are explained by his coming from 
pioneer stock. A boy's ingenuity with mechanical toys 
is regarded as only natural when one finds that he is 
descended from a "long line" of boat builders and in- 
ventors. Nor is this type of interpretation limited to 
popular slip-shod thinking and everyday conversation. 
Many otherwise accurate and well-conducted scientific 
investigations on family resemblances contain the same 
logical fallacy. 

The two major methods employed in the study of family 
similarities and differences are family history and cor- 
relation. The former method has been applied chiefly by 
eugenicists. Geneologies are traced and elaborate pedigree 
charts drawn up for families outstanding either for their 
deficiencies or for their talents. The correlation studies 
usually deal with the scores of relatives on standardized 
tests. Parents and children, siblings, and twins have been 
compared by this method. The correlation coefficient 1 
furnishes a convenient numerical index of the degree of 
correspondence between the scores of any such groups. 

It is of course impossible to determine directly by either 
ofjthese methods what is the relative contribution of hered- 
itaryjDr environmental factors in producing, the xthtained 
similarities. Both methods are at best descriptive and 
serve only to discover more or less objectively the degree 

1 The correlation coefficient (r) is an index of relationship between two sets of 
measures. It varies from +-LOO, a perfect positive correlation, through o, to 
i.oo, a perfect negative or inverse correlation. A +1.00 correlation means 
that the highest score in the one set of measures is paired off with the highest 
in the other set, the second highest in the first with the second highest in the 
second, etc. A i.oo correlation indicates that the highest score in one group 
corresponds to the lowest in the other, a similar, perfect reversal occurring 
throughout the distribution. A zero correlation indicates no relation at all, or 
the sort of arrangement which would result if the scores in the two sets were to 
be shuffled and paired off at random. 


of familial resemblance existing under present-day con- 
ditions of living. Only the experimental approach could 
yield a conclusive solution to this problem. Thus if a 
child of known parentage were isolated from its family 
immediately after birth and brought up under rigidly con- 
trolled conditions, many of the questions on heredity and 
environment might be answered. In such an experiment, 
it would also be necessary to exert some control over pre- 
natal environment, such as by proper care and diet of the 
mother. Unfortunately, popular sentiment and social 
custom have stood in the way of any sufficiently extensive 
experimentation along these lines. An_ajproximation to 
this set-up is,,,,, however, afforded by the study of foster 
children. The earlier the child is adopted, the more nearly 
does this situation resemble the experimental situation 
described above. An excellent opportunity for the analysis 
of hereditary and environmental factors is also furnished 
by identical twins who have been reared apart from an 
early age, although the number of such cases is necessarily 

Because of their more direct bearing upon the heredity- 
environment problem, all studies on twins and on foster 
children have been reserved for a detailed treatment in 
the next chapter. The present chapter will deal exclusively 
with the more common and general sort of family rela- 
tionships, including parents and children, siblings, and 
more remote relatives or ancestors. 


Prompted by his interest in eugenics and the control of 
human evolution, and by his desire to unearth all possible 
data bearing on the laws of human inheritance, 

This method was employed by Galton in his extensive 


investigations on the inheritance of genius, the results of 
which were brought together in 1869 in a book entitled 
Hereditary Genius. Galtori's approach was distinctly 
heredfitarian, as is illustrated by the following summary 
of the aim of his investigation: "I propose to show in 
this book that a man's natural abilities are derived by 
inheritance, under exactly the same limitations as are the 
form and physical features of the whole organic world" 

(Si P- *); 
In this investigation, data were collected on 997 eminent 

men in 300 families. In order to facilitate the tracing of 
family histories and the location of descendants and other 
relatives, the study was limited to eminent men who were 
either English or well-known in England. The informa- 
tion was obtained from biographical collections or through 
direct inquiry among relatives and acquaintances of the 
men themselves. Galton defined as follows the degree of 
eminence necessary for inclusion in his survey: "When I 
speak of an eminent man, I mean one who has achieved 
a position that is attained by only 250, persons in each 
million of men, or by one person in each 4000" (5, p. 9). 
The classes of men in Galton' s survey comprised English 
judges, 1 statesmen, commanders, literary men, scientists, 
poets, artists (musicians and painters), and protestant 
divines, the last including men who had achieved fame 
through some phase of religious activity, such as theolog- 
ical scholars, administrators, religious leaders, martyrs, 

man was taken 

kinships were expressed in 
Following the nameTof each of these men, 
Galton appended a list of famQus relatives together with 
the major field in which each had achieved distinction. 

1 The only category limited exclusively to England. 



Whenever more complete information was available, these 
data were presented in the form of a family chart, a device 
which has gained in popularity among present-day eugen- 
icists. As a final summary of his findings, Galton computed 
the, percentage of eminent men in each degree of kinship 
to the most eminent man of the family, the latter still 
S HZ1BJL S ,, ^ e Pi nt f reference. These percentages are 
given in Table III for each class of "eminence" sepa- 
rately, as well as for all classes combined. It should be 
noted that the eminent relatives within any class have 
not necessarily achieved distinction in that particular 
class; thus the famous kinsmen of a statesman may in~ 


(After Galton, 5, p, 308) 

Nature of Kinship * 










































































, 4 











, *4 


2 * 

















, .4 


First cousin 


















' 10* 









: o 


All more remote 




IS , 






* No female relatives are included in these summary figures, although the 
names and achievements of such relatives are given in the specific family his- 
tories, s ... ' " 


elude scientists, artists, divines, etc. The classification is 
based solely on the field of activity of the "most eminent' 9 
man in the family, around whom the data are organized. 

These figures suggest quite strongly that eminence tends 
to fun In families. Not only are the percentages much 
greater than is expected by chance and quite consistent 
from class to class, but they also show a definite decrease 
in the frequency of eminent relatives as the degree of re- 
lationship becomes more remote. It is quite a different 
matter, however, to conclude that genius is Inherited. 
Galton, to be sure, recognized the difficulties in the way 
of such a conclusion and attempted a systematic analysis 
of them. To the question of whether reputation is a fair 
test of ability, he answers in the affirmative. He argues 
that reputation or eminence, as the criterion is employed 
in his survey, is "the opinion of contemporaries, revised 
by posterity the favorable result of a critical analysis 
of each man's character, by many biographers" (5, p. 33), 
and hence not an accidental rise to short-lived notoriety. 
Natural ability he defines quite circularly as "those qual- 
ities of intellect and disposition, which urge and qualify a 
nan to perform acts that lead to reputation" (5, p. 33). 

Although admitting the influence of training, surround- 
ings, and opportunities, Galton minimizes the part which 
they play in the attainment of eminence. He constantly 
holds up to the reader the heroic picture of genius triumph- 
ing over obstacles. By definition, genius means to him 
"a nature which, when left to itself, will, urged by an 
inherent stimulus, climb the path that leads to emi- 
nence, and has strength to reach the summit one which, 
if hindered or thwarted, will fret and strive until the 
hindrance is overcome, and it is again free to follow its 
labour-loving instinct" (5, pp. 33-34). He concludes that 
" It is almost a contradiction in terms, to doubt that such 


men will generally become eminent/' and adds that " there 
is plenty of evidence in this volume to show that few have 
won high reputations without possessing these peculiar 
gifts" (5, p. 34). This is true enough, but it remains to be 
proved that such "gifts" as the impulse to climb, the 
strength to reach the summit, and the love of labor are 
themselves independent of environment. Unfortunately, 
the optimistic picture painted, by Galton is not borne out 
t>y observations of everyday life; and in the absence of 
experimental proof, it is impossible to accept Galton's 
interpretations of his findings. 1 


The family history method has also been widely em- 
ployed in the effort to analyze the causes of intellectual 
defect, crime, pauperism, and similar conditions. By this 
method, a number of families have been discovered which 
present an overwhelming array of socially inadequate per- 
sons over several generations. The same general tech- 
niques are used in tracing the history of these families as 
in the study of eminent groups. Living relatives or de- 
scendants are visited and observed, residents of the vicin- 
ity are interviewed, and certificates of marriage and birth, 
and similar public records are examined whenever avail- 
able. These families are usually found in rural districts 
in many parts of the country, often inhabiting the same 
crude huts built by their ancestors many generations ago. 
They frequently interbreed, are quite prolific, and even- 
tually come to constitute their own community, shunned 
and ridiculed by their neighbors. 

The earliest published pedigree of such a "degenerate" 

1 Other studies on eminent families will be found in Ch. XIII on Genius. 
Galton's study is here reported only as an illustration of the family history 








Key to Symbols 

Feebleminded Man % 
Feebleminded Woman 
A/ Normal 




(A) Normal Woman v 

(After Goddard, 7, p. 36.) 



dard constantly emphasizes the role of heredity. Having 
laid great stress upon the fact that the two groups were 
branches of the same family, furnishing, "as it were, a 
natural experiment with a normal branch with which to 
compare our defective side," he states that "from this 
comparison, the conclusion is inevitable that all this de- 
generacy- has come as the result of the defective mentality 
and bad blood having been brought into the normal 
family of good blood" (7, pp. 68-69). It seems rather 
curious that the common descent of the two branches 
from Martin Kallikak should be regarded as strengthen- 
ing an hereditary interpretation of the differences be- 
tween them. The environments of the two groups were 
not in any way equated by this common ancestry and 
in fact, it is evident that the members of the two 
branches were reared under widely differing conditions. 
Common descent from Martin Kallikak simply made 
the heredity of the two groups more alike than would 
be the case in the comparison of two distinct families 
and thus seems to strengthen an environmental explana- 
tion of tKe differences, if it contributes anything at 

A more crucial test would have been available if the 
legitimate offspring of Martin and his well-born wife had 
been exchanged at birth with those of the feebleminded 
woman. It would then have been very illuminating to 
ascertain the relative percentage of feeblemindedness and 
other defects in the "normal" and "degenerate" stock. 
The practical obstacles in the way of such a procedure in 
no way strengthen the validity of conclusions drawn from 
an inadequately controlled situation. 

Many equally "degenerate" families have been subse- 
quently investigated by psychologists, sociologists, or eu- 
genicists. The research staff of the Eugenics Record 


Office 1 conducts such surveys as one phase of their regular 
work. Among the groups they have studied are the 
Hill Folk, the Nam family, and the W family of Indiana, 
all presenting the same picture of degeneracy, mental 
defect, disease, and social incompetence through suc- 
cessive generations. Surveys of eminent families have 
likewise been sponsored by the Eugenics Record Office. 
Specific lines of achievement, such as scholarly pursuits 
or boat designing, have been traced from generation to 
generation in the attempt to show that such talents 
are transmitted through heredity. Although offering much 
interesting material, such studies cannot yield any data 
on the heredity-environment question; the opportunities 
for environmental transmission of such family qualities 
are too obvious to overlook or dismiss. 


the correlation technique, although more 
accurate and quantitative, does not eliminate the essen- 
tiaL.jdrfficuIfy inherent . in the family history . ^method, 
naively., the confusion of hereditary and environmental 
CQiLtribiitioi\s. Pearson (14) was among the first to apply 
correlation analysis to parent-child resemblances. Con- 
tinuing a line 'Bf research initiated by Galton (6), he col- 
lected measures on A ^^ garents and offspring in physical 
traits such as stature, arm span, and forearm Je&gth. 
ThE_|)ajeat--cliild correlations in these traits' averaged 
about .52. The similarity of this correlation to those 
oBlamed for bodily characteristics of many animal forms 
led Pearson and others to suggest thal^his^figure indi- 

of ^here.dit^x J^ c ,tor& -to. -the! de- 
Family resemblance in 

1 Eugenics Record Office, Cold Spring Harbor, Long Island, N. Y. Cf., e.g., 
references (i) and (4). 


such traits Is doubtlessly owing in large part to the infly- 
ence of common heredity, "although., the, xole ,of . similar 
environment, especially in the prenatal stage, cannot be 

A crude but frequently quoted early study on parental 
resemblance in psychological traits is that of Woods (19) 
on royal families. Because of the large amount of inbreed- 
ing among royal houses, such a group seemed to offer an 
especially good opportunity for the analysis of family 
likenesses. In addition, genealogies could be traced more 
easily in royalty, and information regarding the char- 
acters and abilities of royal personages was relatively 
accessible. Each individual investigated was assigned a 
rating from I to 10, representing different degrees of in- 
tellect from feeblemindedness to genius. By a similar 
procedure, each was rated for moral qualities. The rat- 
ings were based upon available historical and biographical 
material and are therefore subject to all the errors in- 
herent in such data, plus a possible error of judgment 
introduced by Woods' own evaluation of the facts. 

In the entire survey, data on several thousand persons 
from various European royal houses were employed. From 
the available information, it proved possible to assign 
ratings on intellectual quality to a total of 671 cases and 
on moral traits to 608. The correlations between the 
ratings of offspring and fathers, grandfathers, and great- 
grandfathers, respectively, are given below. 1 

Relationship Intellect Morals 
Fathers and offspring .30 .30 

Grandfathers and offspring .16 .18 

Great-grandfathers and offspring .15 

1 These correlation coefficients, although utilizing the ratings on the lo-point 
scale, were computed by means of a four-fold correlation table. All individuals 
receiving ratings from I to 5 were classified as below average, those between 6 
and 10 as above average. 


That there exists a noticeable correspondence and that 
this correspondence is stronger the closer the relation- 
ship, seems clear from these correlations. Little, can be 
concluded, however, regarding the amount of relation- 
ship, since* the size of a correlation coefficient is too largely 
influenced by -such. errors, of measurement as were present 
in these data. 

More recently, scores obtained by parents and children 
on standardized tests have been correlated, .Jones (n) 
adrninistered intelligence tests to over 300 families in, a 
rural district, in New England. In order to minimize the 
factors of language handicap and differential group tradi- 
tions, communities were chosen in which the population 
was composed entirely of native-born stock. All children 
between the ages of 3 and 14 were given the Stanford- 
Binet; older offspring and all parents were tested with the 
Army Alpha. In 105 families, it was possible to test both 
parents and two or more children. It was upon this 
sampling, consisting of 210 parents and 317 children, 
that the parent-child correlations were computed. 

The following are some of the correlations 1 reported 
by Jones. 

n , Son and 

son Daughter r> 7j 

6 Daughter 

Father .524 .505 ,509 

Mother .544 .557 " .548 

The corrfil&tions-QfrJi^ i.e., father 

and, .spri, or mother aiuL-daughter, ara,~aaL,,,sigi]diip,antly 
higher % than those, .between unlike-sex- pareat ..and. child. 

1 It is a. frequent practice, in studies on parent-child resemblance, to compute 
a "midparent "-child correlation, in which the average score of the two parents 
is correlated with the child's score in order to furnish a final summary measure 
of relationship. Such a correlation is, however, misleading, because in the process 
of averaging scores a certain amount of individual variation is eliminated and as 
a result the correlation may be too high. 


Thusjthere seemed to bejio basis, to the belief that boys 
tend to resemble more closely their fathers, and girls 
their mothers in intellectual level. There was 3 however, a 
small but consistent tendency for the scores of children 
of either sex to correlate more highly with the mother's 
score than with that of the father. This might be at- 
tributed to the closer contact which the mother has with 
the children. 

In a similar study by \Yillqughby (17) eleven tests were 
administered to about 141 children, 100 mothers, and 
90 fathers, all of whom lived in the vicinity of Palo Alto, 
California. The tests ranged from highly verbal to highly 
non-verbal, and were selected from various current scales 
for the measurement of intelligence and scholastic achieve- 
ment. The average of the parent-child correlations in all 
of the tests was .35. There was no consistent tendency 
for the correlations to be higher with either parent. A 
comparison of the correlations on each test, however, 
reveals large discrepancies. The average parental corre- 
lations 1 on different tests ranged from .17 to, .48. When 
the tests were classified into verbal and non-verbal, the 
average parental correlation was .39 for the former and .30 
for the latter. This difference is also borne out by a com- 
parison of individual tests. Thus the three highest cor- 
relations., ^ere. obtained with rdat|y,ely abstract, tests in 
which learning and past experience predominate, viz., 
history-literature information (.48), number-series comple- 
tion (.42), and analogies (.41); the three yielding the 
lowest correlations were checking similarities (.17), geo- 
metric forms test from Army Beta (.28), and symbol- 
digit code learning test, also from Army Beta (.30). 

The results of ,W^illoughby again suggest the 

1 Average of the following separate correlations: mother-daughter, mother-soa, 
father-daughter, and father-son. 


by environment and stimulation in determining the degree 
of familial resemblance. Performance on verbal tests is 
more susceptible to training and home conditions than is 
performance on the non-verbal, and it is the former which 
yielded the highest parental correlations. In Willoughby's 
study, furthermore, the correlations run lower than those 
of Jones. This, too, would be expected from the nature of 
the tests, since the latter used only intelligence tests of a 
highly verbal type. The fact that Jones correlated total 
scores on composite tests made up of many parts, whereas 
Willoughby employed scores on single and fairly homo- 
geneous tests, may also account for the higher correla- 
tions found by Jones. The more complex the measures 
correlated, the greater are the chances .that they..^ill 
have common elements and the higher will their inter- 
correlations tend to be. 

Certain tentative conclusions are suggested by an anal- 
ysis of the data on parental resemblance. In the first 
place, parents and children exhibit a distinct similarity 
in physical traits, which r&ay b<e expressed by a correla- 
tion in the neighborhood of .50. Approximately the sai^e 
degree of correspondence is found on most .common in- 
telligence tests of t the verbal type, \yhen, however, Qpm- 
parisons are made on more homogeneous .tests^Qi^on 
tests which are less susceptible to common home environ- 

' "' '" A ' ,,,,<?< P -. 

ment, the correlations are much lower. There is a sug- 
gestion of a closer resemblance to the mother than to the 
father in intelligence test performance, although the data 
on this point are inconclusive. 


Investigations on the resemblance of siblings have been 
much more numerous than those on parent-child similar- 
ity. As Pearson pointed out, the comparison of siblings, 


especially when both are in school, does not present the 
practical difficulties met in the testing or rating of parents. 
In addition to extensive comparisons of siblings in physical 
traits such as eye-color., hair-color and curliness, health, 
and head dimensions, in which about the same degree of 
relationship was found as in the parent-child studies, 
Pearson (13) undertook an investigation of, .sibling re- 
semblances in mental traits. The data of the latter study 
consisted exclusively of teachers' ratings on schoolchildren. 
The measures used are necessarily crude and may be 
biased by the teachers 5 own reaction to family relation- 
ships; thus, two brothers might be rated more nearly 
alike because the teacher knows that they come from the 
same family. The correlations are based on large sam- 
plings, however, the number of cases varying from 554 
to 2152 for different traits. Below are the correlations 
found by Pearson between pairs of brothers, pairs of 
sisters, and mixed pairs, consisting of a brother and a 

Trait Brothers Sisters Mixed Pairs 

Vivacity 47 .64 .63 

Self-assertiveness .53 .49 .51 

Popularity .50 .56 .48 

Conscientiousness .59 .61 .52 

Temper .51 43 49 

Ability 46 44 .52 

Handwriting .53 47 .63 

Introspection .59 47 44 

Average .52 .57 .49 

Pearson himself gives a strongly hereditarian interpreta- 
tiorTto these findings, offering the opinion that: "Jt. js, the 

stockjtself wjiich f makes its^ home^aiv^^ 
cation is of small service^ul^&lV^ 

gent rrc^Slmen* y (13, p. 159). It is characteristic of many 
- t | ie influence of environment is min- 


imized, to cite formal education as the principal environ- 
mental force and to overlook the broader and probably 
more effective aspects of general environment. Since 
Pearson found very similar sibling correlations in mental 
anct physical traits, and .since, he believed the latter could 
beTIttie influenced by environment, he concluded that 
thelame must be true of mental traits. Such a conclusion 
doesTiot necessarily follow. It is itself based on the as- 
sumption that mental and physical traits are inherited in 
the same manner and thus involves a circular argument. 

Investigations with mental tests have all yielded posi- 
tive and significant sibling correlations, although the 
amount of relationship varies with the particular test, 
the age of the subjects, and other conditions. Gordon (8) 
found a correlation of .53 between the Stanford-Binet 
I.Q.'s of 91 pairs of siblings in an orphanage in California. 
Pintner (15) administered six simple tests to 180 pairs of 
siblings and computed "mental indices" for each child on 
the basis of scores on all the tests; the sibling correlation 
in mental indices was .22. Hart (9) correlated the I.Q.'s 
of siblings in three groups of schoolchildren, the number 
of sibling pairs in each group being 252, 147, and 219, 
respectively. The I.Q/s were found from scores on Army 
Alpha, National Intelligence Test, and Stanford-Binet. 
Correlations of .447, .459, and .399 were obtained in the 
three groups. 

In an extensive investigation of sibling resemblance, 
Hildreth (10) analyzed the LQ.'s of three large groups of 
schoolcKildren. The first group consisted of 671 public 
schoolchildren from 300 families in Oklahoma City; this 
was a group of average social status. The second group 
was composed of 523 children attending the Horace Mann 
School in New York City, the number of families repre- 
sented totaling 241; the social and cultural level of this 


group was definitely superior. The third was a group of 
inferior social status obtained from the Hebrew Orphan 
Asylum in New York City; it included 346 children in 
146 families. The number of siblings within any single 
family ranged from two to five. The I.Q.'s were based 
on some form of the Binet scales, about 98% of them 
having been obtained with the Stanford Revision. 

The sibling correlations in each of the three groups, 
in the order named above^ were .629, .274, and ,322, 
respectively. The variation from group to group is large, 
especially since the same test was employed. The discrep- 
ancies probably result chiefly from differences in hetero- 
geneity^of tHe^giaups. TheJHprace Mann group, being 
thFmost highly select and homogeneous, gave the lowest 
correlation, whereas the Oklahoma group, a more nearly 
random sample than either of the other two, yielded the 
highest correlation. In general, the wider the range of 
individual differences within a group, the higher will be 
the correlations. 1 Hildreth concludes that the sibling 
correlation in intelligence would "certainly appear to be 
greater than .3 and less than .7" (10, p. 56), and proposes 
" heredity rather than environment as the cause of the 
resemblance found" (10, p. 60), although admitting that 
the data relevant to the latter point are fairly scant. 

Thorndike (16) reported a correlation 2 of .60 between 
the scores of about 1200 pairs of siblings on the I.E.R. 
Tests of Selective and Relational Thinking, Generaliza- 
tion, and Organization. 3 Since all of the subjects were 

1 For a fuller discussion of the effect of homogeneity of the sampling upon the 
size of a correlation coefficient, the reader is referred to Ch. XI. 

2 The value given (.60) was estimated by Thorndike after applying corrections 
for selective factors and other conditions, 

3 A series of tests of the type usually found in intelligence scales, including 
opposites, analogies, sentence completion, arithmetic reasoning, number series 
completion, etc. They have an added advantage in that the scores are expressed 
in terms of an equal unit scale. 


attending high school, this group is older and more select 
than those ordinarily employed in other sibling studies. 
In interpreting his findings, Thorndike follows the argu- 
ment originally proposed by Pearson (cf. above). Thus 
he concludes that the difference of .08 between the cor- 
relation of .60 on the LE.R. test and that of .52 estab- 
lished by Pearson (13) for physical resemblances in sib- 
lings may be attributed to the equalizing influence of 
similar school environment. This would only follow if the 
influence of heredity upon mental traits were known to be 
identical to its influence upon physical traits, and if in 
addition it could be assumed that physical traits develop 
incomplete independence of environmental factors. 

Willoughby (17), in his investigation of family resem- 
blance cited in the preceding section, also obtained data 
on sibling relationships in the eleven mental tests which 
he administered. The subjects for this part of the study 
were 280 siblings, ranging in age from seven up. The 
average and range of the correlation coefficients for the 
different tests were as follows : 

Average i 
(j/ Tests) 

Average r 

Average r 

Range in r 




.18 to .58 




.26 to .63 




.24 to .54 

Unlike-sex siblings 

It u is noteworthy that the like-sex siblings gave higher 
correlations thai tte unllkersex. This difference, although 
small, suggests the greater community, pf .environment 
furnished, within the family for like-sex siblings. As was 
the case with parental correlations, the sibling correlations 
exhibit a pronounced variation from test to test, and in 
two of the three sibling groups, the average correlation is 
higher for the verbal than for the non-verbal tests. 


In their extensive investigations of honesty In school- 
children, May and Hartshorne (12) computed sibling 
correlations on four types of deception tests. A total of 
734 pairs of siblings in seven groups were measured. The 
correlations, 1 differing somewhat with the group and the 
test, ranged from .208 to 445. May and Hartshorne min- 
imize the part played by environment in these sibling 
resemblances, their main argument resting on the finding 
that socio-economic level of the home did not correlate 
very highly with honesty scores. Other less easily ob- 
servable aspects of home environment may, however, be 
much more significant than socio-economic level in the 
development of such character traits. 

It would seem that the correlations in test performance 
oFlsTblings reared together, although uniformly positive 
arid" reliable, show a marked variation in amount. Among 
the major factors which determine this variation may be 
mentioned the nature of the test and in particular its 
relative dependence upon environment and training, the 
homogeneity of the sampling, and the age of the subjects. 
In regard to the factor of age, it is apparent that the older 
the subjects, the longer will environmental influences have- 
been operative. Whether such influences will have a 
leveling or a differentiating effect, however, will depend 
upon the specific circumstances in each case. 


1. Danielson, F. H., and Davenport, C. B. The Hill Folk. 
Cold Spring Harbor: Eugenics Record Office Memoir No. I, 
1912. Pp. 56. 

2. Dugdale, R. L. The Jukes: a Study in Crime, Pauperism, 

1 One type of deceptive behavior, mz., securing help contrary to instructions 
on a test taken at home, gave much higher sibling correlations, but this was 
definitely affected by collusion, the siblings either helping one another or en- 
couraging each other in the use of forbidden aids. 


Disease, and Heredity. N. Y.: Putnam, 1910 (ist ed. 1877). 
Pp. 1 20. 

3. Estabrook, A. H. The Jukes in 1915. Washington: Carnegie 
Institution, 1916. Pp. 85. 

4. Estabrook, A. H., and Davenport, C. B. The Nam Family, 
Cold Spring Harbor: Eugenics Record Office Memoir No. 2, 
1912. Pp. 85. 

5. Galton, F. Hereditary Genius: an Inquiry into Its Laws and 
Consequences. London: Macmillan, 1914. Pp.368. 

6. . Natural Inheritance. London: Macmillan, 1889. Pp. 


7. Goddard, H. H. The Kallikak Family: a Study in the Hered- 
ity of Feeblemindedness. N. Y.: Macmillan, 1921 (ist ed. 
1912). Pp. 121. 

8. Gordon, K. "Psychological Tests of Orphan Children," 
J.Del., 1919, 4, 46-55. 

9. Hart, H. "Correlations between Intelligence Quotients of 
Siblings," Sch. and Soc., 1924, 20, 382. 

10. Hildreth, G. H. "The Resemblance of Siblings in Intelli- 
gence and Achievement," Teachers College, Columbia Univ., 
Contrib. to Educ., 1925, No. 186. Pp. 65. 

11. Jones, H. E. "A First Study of Parent-Child Resemblance 
in Intelligence," 2fih Yearbook, Nat. Soc. Stud. Educ., 1928, 
Part I, 61-72. 

12. May, M. A., and Hartshorne, H. "Sibling Resemblance in 
Deception," 2jth Yearbook, Nat. Soc. Stud. Educ., 1928, 
Part II, 161-177. 

13. Pearson, K. "On the Laws of Inheritance in Man: II. On 
the Inheritance of the Mental and Moral Characters in 
Man, and Its Comparison with the Inheritance of Phys- 
ical Characters," Biom., 1904, 3, 131-190. 

14. Pearson, K., and Lee, A. "On the Laws of Inheritance in 
Man: I. Inheritance of Physical Characters," Biom., 1903, 
2, 3S7-462. 

15. Pintner, R. "The Mental Indices of Siblings," Psychol 
Rev., 1918, 25, 252-255. 

16. Thorndike, E. L., and staff. "The Resemblance of Siblings 


in Intelligence," 2fth Yearbook, Nat. Soc. Stud. Educ. } 
1928, Part 1,41-53. 

17. Willoughby, R, R. "Family Similarities in Mental Test 
Abilities," 27th Yearbook, Nat. Soc. Stud. Educ., 1928, 
Part I, 55-59. 

1 8. Winship, A. E. Jukes-Edwards: a Study in Education and 
Heredity. Harrisburg, Pa.: Myers, 1900. Pp.88. 

19. Woods, F. A. Mental and Moral Heredity in Royalty. 
N.Y.: Holt, 1906. Pp. 3 12. 


In the present chapter, a survey of psychological 
studies on twins and foster children will be presented. 
These two types of investigation of familial resemblance 
have been selected for a more detailed treatment because 
of the special facilities which they offer for the analysis 
of the relative contribution of hereditary and environ- 
mental factors. Twins and foster children may be said to 
represent the two extremes of hereditary similarity. In 
the case of identical twins, heredity is completely alike for 
the two individuals, so that any differences between them 
may_be attributed "directly to the operation of different 
stimulating conditions. Fotfer^ children) on the other 
ha.nd 3 bear no hereditary resemblance to their adopted 
parents or to any other children with whom they are 
reared. These subjects therefore, Reveal the contribution 
of environmental influences in any similarity which they 
may exhibit to their foster parents or foster siblings. 

The observation and measurement of fraternal or non- 
identical twins also offer a fruitful approach to this general 
problem. Such twins are no more alike than ordinary 
siblings in respect to heredity. They have, however, been 
exposed to the same prenatal environment. Since they 
are of the same age, they are also subjected to postnatal 
stimulation which is much more similar than in the case 
of ordinary siblings. They would thus seem to offer a 
sort of "environmental control" in the analysis of the 
sibling resemblances ordinarily observed. Similarly, the 
cases of identical twins who have lived apart from early 



infancy may be regarded as an " hereditary control" for 
identical twins reared together in the usual way. Both 
of these groups have the same degree of hereditary com- 
munity; any differences in amount of resemblance are 
therefore attributable directly to environmental varia- 


Twins have long been acclaimed as particularly good 
material for the analysis of behavioral resemblance. 1 The 
arguments which have been put forth in the effort to 
prove the major potency of -heredity on the basis of twin 
resemblance., summarized under five headings. 
A brief critical evaluation of each will be given. 

guiXLent ,is based on the relative degree of 
pf siblings. The closer resem- 
blance of the former cannot, however, be attributed in- 
discriminately to their more similar heredity. It is true 
that, in respect to general home background and school- 
ing, the environment of siblings is about as similar as 
that of twins. But the attitude of the parents towards an 
older and a younger sibling, the attitude of the children 
towards each other, and the specific events and vicissi- 
tudes occurring at any one life period for each child will 
differ far more for siblings than for twins. Conditions of 
this sort, operating differentially from a very early age, 
may be even more important than economic level or 
formal schooling in the development of the child's men- 
tality and character. 

Ajsecpnd type of cpmparison is that 

I* * s ften Argued that if environment 
were a significant factor in the resemblance of twins, 
then this resemblance should be closer in the older twins 

1 For a discussion of the biology and physiology of twins, cf. Newman (10, n). 


who have been exposed for a longer period to the equaliz- 
ing environmental influences. As has been repeatedly 
pointed out above, however, it is impossible to generalize 
regarding the particular direction which environmental 
influences will take. Thus it seems very probable that in 
the case of twins, early environment may have a strongly 
equalizing eifect, whereas later environment may produce 
differentiation. Prenatal environment, to be sure, is 
very similar in such cases. In infancy and early child- 
hood, the twins are usually treated in much the same way. 
As the children grow older, however, any differences be- 
tween them tend to be noted and emphasized for practical 
reasons, and the twin begins to learn that he must lead 
his own life and develop as an individual if he is to be 
well-adjusted. It would seem that a drop, rather than a 
rise, in correlation with age is to be expected on environ- 
mental grounds. 

In some of the more recent studies the attempt 
has been made to classify twins into identical and non- 
identical, or fraternal. The comparison of these two types 
of twins in mental traits has furnished a third approach 
to the analysis of hereditary and environmental factors. 
It will be recalled that identical twins develop from a 
single fertilized ovum and therefore have identical hered- 
ity, whereas fraternal twins are no more similar than 
ordinary siblings in their hereditary constitution, although 
they develop simultaneously. It would seem that the 
difference in degree of resemblance of identical and non- 
identical twins could be attributed directly to heredity. 
The environment of fraternal twins is doubtlessly more 
uniform than that of siblings born at different times. 
But is it necessarily as homogeneous as that of identical 
twins? It must be remembered that fraternal twins are 
often of unlike sex, and the differential treatment of the 


two sexes may enter in to render their environment dis- 
similar. This may prove a very potent differentiating 
influence in the development of the two children. The 
physical differences themselves which characterize the 
fraternal as contrasted with the identical twins may 
further encourage differential reactions towards the 
former, especially during the important earlier ages when 
the identical twins are probably still being confused by 
their associates. 

A fourth analysis is based upon the relative degree of 
twin resemblance in traits differing in their susceptibility 
to training. Such a comparison is very illuminating, 
provided the traits are not simply classified in respect to 
their dependence upon school training. Home environ- 
ment is far more significant than formal schooling in de- 
termining twin or any other family resemblance. In those 
tests which depend primarily upon school training, we 
should expect unrelated children to resemble each other 
nearly as much as related children. This is especially 
true in studies in which all of the subjects are in the same 
community and hence exposed to fairly uniform schooling. 

Lastly, twin resemblances in mental and in physical 
traits have been, compared. A similarity in degree of 
correlation in the two cases is customarily regarded as 
evidence that the mental resemblances are independent 
of environment. This is based on the argument proposed 
by Pearson in his discussion of sibling correlations. The 
fallacy inherent in such a conclusion has already been 
discussed in the preceding chapter. 


As early as 1875, Galton (3) compared the character- 
istics of about 80 pairs of twins, by means of question- 
naires. The first quantitative investigation on the mental 


resemblance of twins was conducted by Thorndike (14), 
Six simple mental tests were administered to 50 pairs of 
twins between the ages of 9 and 15, and to a similar 
group of siblings. 1 On 39 of the twin pairs physical 
measurements were also obtained for comparative pur- 
poses. The correlations on the entire group of twins 
range from .69 (cancellation of A's) to .90 (naming oppo- 
sites of words). The Correlations are higher, in general, 
in those tests more susceptible to home surroundings and 
cultural level. 

Sibling correlations were found on only three of the six 
tests and were all much lower than the corresponding 
twin correlations, their values being .32, .29, and .30. The 
twins were further classified into an older (age 12-14) an< 3 
a younger group (age 9-11). Th&Avgfcage correlations^ 
.70, for .the older and .83 for the younger. Finally, the 
average twin correlation on eight physical traits proved 
to be .765 as compared to an average of .78 for the mental 
traits. Thorndike gave a strongly hereditarian interpre- 
tation to all of these findings, relying upon the arguments 
outlined above. 

Lauterbach (5), who tested 212 pairs of twins with 
eight mental tests and in addition obtained several physi- 
cal measures on them, reports an average correlation of 
.67 between like-sex 2 twins and .41 between unlike-sex 
or fraternal twins in mental traits. The average correla- 
tion for older twins (157-328 months) was .55 and for 
younger (90-156 months) .54. The resemblances were 
higher, on the whole, in physical traits, the average cor- 
relation in four such traits being .77 and .55 for like-sex 
and unlike-sex groups, respectively. 

Merriman (8) tested 200 pairs of twins with the Stan- 
ford-Binet, National Intelligence Test, and a modified 

1 Number and age not specified. 2 Probably identical twins in most cases. 


form of Army Beta. 1 Separate correlations were computed 
for like-sex and unlike-sex twins, as well as for a younger 
(5-9 years) and an older (10-16 years) group. The correla- 
tions of the entire group were very close to .80 on all three 
tests. Like-sex twins gave consistently higher correlations 
than unlike-sex, their correlations on the Stanford-Binet 
being .867 and .504, respectively, on the National Intelli- 
gence Test .925 and .867, and on Army Beta .908 and ,732. 
In the majority of comparisons, the correlations were 
higher in the younger than in the older group, although the 
number of cases employed in these correlations was fre- 
quently small and inconsistencies were necessarily present. 
In an investigation on identical and non-identical 
twins, Tallman (13) administered the Stanford-Binet to 
158 pairs of twins and 199 siblings between the ages of 
3 and 20. The average difference in I.Q. between the 
siblings was 13.14, and this dropped to 11.96 when only 
siblings who were less than two years apart in chronologi- 
cal age were included. In computing the average differ- 
ence between twins, Tallman combined her data with 
those of Merriman 2 and obtained a final average of 7.07, 
only about one-half as large as the sibling difference. In 
this combined group, there were 84 pairs of unlike-sex 
twins. The average I.Q. difference of these twins was 8.48. 
The like-sex group contained 178 pairs and gave an aver- 
age difference of 642. In the like-sex group, 63 pairs were 
classified as identical twins, on the basis of general physi- 
cal resemblance as well as coloring of hair, eyes, and skin. 
The average difference of these identical twins was 5.08, 
as contrasted to a difference of 7.37 for 39 non-identical 
twins in the like-sex group. 

1 Not'all of the children took all three tests. 

2 Cf. above; 105 pairs of twins in Merriman's group were given the Stanford- 


Hirsch (4) reports an average I.Q. difference of 13.8 
points between 58 pairs of "dissimilar" or fraternal 
twins, and 2,3 points between 38 pairs of "similar" 1 twins. 
Correlations of I.Q.'s were .97 for similar and .53 for dis- 
similar twins. These findings, together with the fact 
that the average I.Q. difference of 4 pairs of similar twins 
living apart was only 3.5 points, led Hirsch to a rather 
strongly hereditarian interpretation. Only the results on 
the twins living apart could, however, be regarded as 
crucial, and these were unfortunately based on very in- 
adequate data. Apart from the small number of cases, a 
serious objection to these data is that the period of separa- 
tion was too short to allow much differentiation. The 
separation, furthermore, occurred so late in life as to have 
practically no significance in the development of the 
individual, the twins in each pair having been first sepa- 
rated at the ages of 12, 18, 29, and 33 years, respec- 

MeNaQHu* (7) administered five tests of motor skills 
to 98 pairs of male twins in junior high school. On the basis 
of physical criteria, 46 pairs were clearly classified as 
fraternal and 47 as identical. The twin correlations 
ranged from .39 to .56 for the fraternal group, and from 
.71 to. .95 for the identical. Continued practice in three 
of the tests produced no significant change in correlation 
in the identical group and a rise on two tests in the fra- 
ternal group. McNemar concludes from these data that 
hereditary factors play the major part, in twin resem- 
blances in motor abilities. Insofar as sensory and muscu- 
lar development is involved in such functions, this finding 
is not especially surprising. In no case, however, could 
snch a conclusion be carried over to otHer kinds of ac- 

1 Probably identical. 



The study of twins reared apart from an early age 
furnishes an excellent opportunity for the analysis of 
hereditary and environmental factors. If the twins are 
identical, heredity can be regarded as constant. The 
operation of similar environmental influences is limited 
to prenatal life and to the brief postnatal period during 
which the twins may have lived together. Although not 
to be ignored, the community of environment in such 
cases is certainly much less than that commonly found 
among twins. Naturally, the number of twins available 
for observation under these conditions is very small. For 
this reason, the case history method has proved the most 
fruitful, since it is best suited to a thorough analysis of 
all the available information on relatively few subjects. 
TJje^first^ report of a pair of identical twins reared apart 
was published in 1925 by Muller (9). The main facts of 
this report are reproduced below. 

A pair of identical female twins were separated at the age 
of two weeks and brought up by different families. The twins 
did not see each other until they were 1 8 years old, and even 
after that age they only met for short visits. At the time of 
examination, they were 30 years of age. The environment 
of the two girls presented certain major differences as well 
as similarities. Twin J completed high school and had some 
summer university work; she has taught school, is married, 
and has a child. Twin B had only four years of formal edu- 
cation. At the age of 15, she took up clerical work and has 
been engaged in an active business career ever since. Her 
foster family moved about a good deal. Twin B did not 
have as many social contacts as her sister. Both read pro- 
fusely as children, and both had been energetic, popular, 
and active in club work in their communities. On Army Alpha 
and Otis Advanced Test of Intelligence, the twins obtained 


very similar scores. Marked differences were found, however, 
on personality tests, speed of free association, and tests of 
motor speed and coordination. The differences were in gen- 
eral such as would be expected from the variations noted in 
their environments. 

Following the report by Muller, there have appeared a 
series of very illuminating case studies by lawman. 1 Nine 
of these have been published to date and more are being 
collected. In all cases the twins have been separated from 
infancy or very early childhood. Psychological tests were 
administered in every instance, so that some quantitative 
data are available to supplement the general observations. 
The findings varied from one case to the other. Some 
twtfr^^wfefe^to'iincl ' who resembled each other in most 
traits; others showed close resemblance in certain char- 
acteristics and differences in others ; and still others exhib- 
ite^'marked discrepancies in all traits, intellectual, emo- 
tional, and even in such physical conditions as general 
health"" ancfbbdily vigor. 

"Thfcse variations are not surprising. The accidental 
separations of everyday life to which a pair of twins may 
be subjected are not to be viewed in the same light as an 
experimentally controlled separation. In the latter, 
every effort would be made to render the environments of the 
pair as unlike as* possible, in order to make the test more 
crucial and the findings more clear-cut. In the cases re- 
ported by Newman, however, a certain element of chance 
entered into the selection of environments. Thus certain 
pairs of twins may have been accidentally adopted into 
homes which differed widely, others reared in surround- 
ings which shared a few important features, and still 

1 For complete accounts, the reader is referred to Newman (12). Freeman and 
Holzinger cooperated with Newman in the psychological parts of these observa- 


others exposed to environments which, although geo- 
graphically separate, may have been fundamentally alike 
in their influence upon the growing child. 

Unless the cultural milieu and educational facilities of 
the children are sufficiently different, one cannot be sure 
that any similarity between them is the result of heredity 
alone. This is particularly true of a degree of ability 
which is not far removed from the average. Thus, hun- 
dreds of children can be found with an LQ. of no, all of 
whom come from different families and live in different 
homes. Nor does equality of score on an intelligence test 
indicate mental identity, since the same total scote may 
be obtained by subjects differing in specific abilities. The 
use of total scores on complex intelligence tests allows 
sufficient leeway to obscure a moderate amount of individ- 
ual variation. The fact that twins reared apart from 
early infancy ^iay"15bTafii very similar LQ-Vdpes not, 
therefore, constitute proof that intelligence is, independ- 
ent of environmental influence. On the other hand, it is 
obvious that even a single case of unmistakable varia- 
tioij^between twins known ,,,to r headentical, in hereditary 
constitution is conclusive evidence that .psyqholpgical 
characteristics are susceptible to environmental factors. 
This is, "in 'Fact, equivalent to stating that if an event 
occurs once, the possibility of its occurrence has been 

As an illustration of Newman's findings, a detailed 
account of two cases is given below. These cases were 
selected because the differences in environment were 
sufficiently large to give clear-cut results. 

CASE IV (12, p. 200): Female twins, separated at the age 
of five months and reared by relatives; 29 years old when 
examined. Mabel had led the life of an active farm woman 
on a prosperous farm. Mary had lived largely a sedentary 


life in a small town, clerking in a store during the day and 
teaching music at night. Mabel had only an elementary school 
education, while Mary had had a complete high school course 
in an excellent city school. At the time of examination, a 
vast difference was noted between the twins in intellectual 7 
emotional, and physical traits. Physically, Mabel is described 
as robust, muscular, and in perfect health, while Mary was 
underweight, soft-muscled, and in poor general condition; 
Mabel weighed 138-5- Ibs., Mary only nof Ibs. Intellectually, 
an equally striking difference was found, but in favor of 
Mary whose Stanford-Binet I.Q. was 106 as compared with 
88 for her sister. Even larger differences were obtained in 
some of the other tests. Temperamentally, these twins are 
described as no more alike than two persons chosen at 

CASE VIII (12, p. 202): Female twins separated at three 
months of age and reared in the home of a maternal uncle 
and the latter's brother-in-law, respectively; examined when 
about 15 years old. M lived in a small town where she knew 
nearly everybody and had many friends and playmates. 
Her foster father was well educated and had a cultured home, 
involving good books, good music, etc. R was brought up 
in a large city, but she was kept closely at home and had few 
friends. Her home environment is described as narrow and 
"unstimulating," neither of her foster parents having had 
much education. Formal schooling differed little in the two 
cases, M being in grade loA and R in loB at the time of exam- 
ination. The physical environment is reported as being about 
the same for both. When examined, the two girls showed a 
remarkable similarity in physical characteristics. Mentally, 
there was a large difference, M doing consistently better 
on all tests. The Stanford-Binet I.Q.'s were 92 and 77 for 
M and R, respectively. Temperamentally, the differences 
were also large, as shown both by scores on personality tests 
and by general behavioral observations. R is described as 
timid and retiring, with a marked lisp in her speech, and 


apparently unhappy. M, on the other hand, seemed quite 
normal in emotional development. 


Another approach to the analysis of heredity and en- 
vironment has been made through the examination of 
large groups of foster children. Three such studies have 
been conducted to date, one by Burks at Stanford Uni- 
versity, another by Freeman and his associates at the 
Univershy of Chicago, and a third and most recent by 
Leahy at the University of Minnesota. Burks and Leahy 
offer rather strongly hereditarian interpretations of their 
findings, whereas Freeman lays much greater stress upon 
environmental factors. A brief analysis of each study 
will throw some light upon the reasons for such apparent 

Burks (i) administered the Stanford-Binet to 214 foster 
children and 382 foster parents, one or both parents being 
tested in each family. A control group of 105 children 
and 205 natural parents were similarly examined. The 
study was carefully controlled from many angles. All of 
the foster children were placed in their adopted homes 
under the age of 12 months, and at the time of testing 
they were between 5 and 14 years of age. The control 
group was quite accurately matched with the foster group 
in respect to age of children and parents, educational, 
occupational, and social status of the parents, and cultural 
level of the home. In both groups, all subjects selected 
for investigation were White, non-Jewish, English-speak- 
ing Americans, British, or North Europeans, and all were 
residents of three districts in California. Each foster 
child lived in the home of a married couple both of whom 
were alive and living together at the time. The same 
specification was applied to the control group. In addi- 


tion to the Stanford-Binet M.A/S, information was ob- 
tained on cultural level of the home, educational, voca- 
tional, and other characteristics of the parents, home 
activities and care of the children, and parents' ratings 
on intellectual and personality traits of the children. 
Data on the natural parents of the adopted children were 
also examined whenever available. 

The correlation between mental ages of parents and 
children in both foster and control groups is reproduced 
below; the correlation between child's mental age and 
cultural index of the home is also given. 

r between Child's M.A. and: Foster Control 

Father's M.A. .07 45 

Mother's M.A. .19 -4^ 

Cultural index of home .25 .44 

From these and similar correlations between child's M.A. 
and various other conditions, Burks concludes that 
heredity is much more important than environment in 
determining individual differences on intelligence tests. 
On the basis of further statistical analyses of the data, 
she estimates that, "the^total^ contribution of Jxeredity 
... is probably not far from 75 or 80 per cent" (p. 308). 
She also suggests that, "The maximal contribution of the 
best home environment to intelligence is apparently about 
20 I.Q. points, or less, and almost surely lies between 10 
and 30 points. Conversely, the least cultured, least stim- 
ulating kind of American home environment may depress 
the I.Q. as much as 20 I.Q. points' 5 (p. 309). 

. Xp.,,tjie,, investigation 4>y- Leaity^(6), t]j& .same general 
procedure was followed as in Burks' study, with a few 
improvements. Thus the Otis Self- Administering Test 
(Intermediate Form) was substituted for the Stanford- 
Binet in testing the parents, this test being better adapted 


to the adult level than the Stanford-Binet. The match- 
ing of the experimental or adopted group with the control 
group was done very meticulously, each adopted child 
being paired with a control child of the same sex, mental 
age (within 6 months), paternal occupation, and father's 
and mother's schooling. All subjects were White,, non- 
Jewish, and of North European extraction. The children 
in both groups were reared in communities of 1000 or 
more inhabitants, 95% of the group living in communities 
of over 10,000. All of the foster children were legally 
adopted by a married couple. The age of adoption was 
placed even lower than in Burks' study, all of the children 
in the experimental group having been placed in the foster 
homes at the age of 6 months or younger. At the time of 
investigation, the children ranged in age from 5 to 14, the 
average ages being 9.3 years for the adopted and 9.4 for 
the control group. There was a total of 194 children in 
*ach group. 

The general results of Leahy's study are in agreement 
with those of Burks. The correlations of child's I.Q. with 
father's and mother's Otis scores and with a cultural index 
Df the home are reproduced below. Corresponding figures 
are shown for foster and control groups. 

r between Child's I.Q. and: Foster Control 

Father's Otis score .19 .51 

Mother's Otis score .24 .51 

Cultural index of home .26 .51 

Various other comparisons were, made which lead the 
mSTor to conclude, with Burks,, that, .heredity ,.. js ^the 
BatOTf aietor in the determination of intellectual level. 1 

J . .. , .,., ' l ' ' " ' '" ,., ,, ., , . ,.u , , . ,--.. , A 

x The Woodworth-Mathews Personal Data Sheet for measuring emotional 
n'stability was also administered to both the experimental and control groups. 
[t is unfortunate, however, that no personality measures were obtained on the 
Darents, with which the children's scores might have been correlated. Curiously 


In spite of the care with which these investigations were 
conducted, there still remain too many disturbing factors 
for a conclusive analysis of hereditary and environmen- 
tal influences. Thus the groups tested were admittedly 
very homogeneous in respect to economic, cultural, and 
educational status. Both Burks and Leahy point out 
that more marked environmental differences might pro- 
duce larger intellectual deviations and that the results 
hold only for children brought up in the general run of 
American homes. 

In the second place, the possibility still remains that a 
group of children living with their natural parents might 
not furnish a perfect control for foster children. The atti- 
tude of foster parents towards a child may differ in some 
essential ways from that of own parents. In some cases* 
the contact of foster parent and child may not be as close 
or intimate as that of a child and his natural parents. 
The fact that in both studies the foster child's mental 
level correlated higher with the cultural index of the home 
than with mother's intellectual level, and higher with the 
latter than with father's intellectual level, whereas all 
three correlations are very similar or identical in the con- 
trol group seems to support such a suggestion. The child 
himself, if he knows of his adoption, may react differently 
towards his foster parents than he would towards his own 
parents. 1 Social expectancy may also enter into and corn- 
enough, Leahy concludes that environment plays a far greater part in the de- 
velopment of personality traits than in the case of intelligence. The basis for 
such a conclusion is the absence of significant correlations in both experimental 
and control groups between Woodworth-Mathews score of child and parent's 
intelligence or cultural index of home. It is difficult to follow the author's logic 
in such a conclusion. Surely we should not expect a very high correlation be- 
tween intellectual and personality traits, regardless of the hereditary or environ- 
mental determination of such traits. 

1 In Burks' group, 35% of the children had been told of their adoption, in 
Leahy's group, 50%, 


plicate the situation. Parents as a rule expect their own 
children to resemble them in intellectual and emotional 
development and this expectation may be manifested 
in their behavior towards the child, as well as In the atti- 
tude of other relatives and associates. As the child de- 
velops, his observers constantly call attention to points 
of family resemblance, real or imagined; he is frequently 
reminded of ancestral characteristics which are held up 
to him as his heritage. Such social influences are absent 
or greatly reduced in the case of foster children. Who 
knows what motivational differences might thereby arise, 
which would subsequently leave their mark upon the 
development of abilities ? 

In another extensive investigation on^ foster children, 
Freeman et al. (2) present data from a variety of compari- 
sons. A total of 401 children was employed. All sub- 
jects were residents of Illinois. Both White and Negro 
children were included, but the number of the latter was 
small The ages at adoption were much higher than in 
Burks' study, although over half of the entire group were 
under three years old when committed. The children were 
tested with the Stanford-Binet and the International 
Group Mental Test; 1 the foster parents were given the 
Otis Self-Administering Test 2 and a specially constructed 
vocabulary test covering many fields of knowledge. Field 
workers collected data on education, vocation, and cul- 
tural level of the foster parents, and conditions of the 
foster home. Information on the natural parents was 
obtained through visits, interviews with acquaintances, 
and examination of case records. 

In order to facilitate various comparisons, the children 

1 Specially devised as a universal test of intelligence and relatively inde- 
pendent of specific cultural environment. 

2 A common verbal group test of intelligence. 


were classified into four overlapping groups, and the major 
results on each reported separately. Group I, the pre-test 
group., consisted of 74 children who had been tested be- 
fore adoption and who had lived in the same foster home 
until the time of the second examination. The average 
age of these children at adoption was eight years. The 
main data furnished by this group relate to gains in score 
from the first to the second testing. The average I.Q. 
showed a small but fairly reliable 1 rise from 91.2 to 93.7. 
When the group is subdivided into those adopted into the 
better and those adopted into the poorer foster homes, the 
former show a clear-cut improvement in I.Q., the latter 
no change. Similarly, the younger children proved more 
susceptible than the older to a change of surroundings. 
The relevant data are summarized below (2, p. 119). 

/> T ? D ,- / v AT Average I.Q. 

Cultural Rating of Home N pim Test gecond Test 

17 to 30 (Better homes) 33 95.2 100.5 

7 to 1 6 (Poorer homes) 41 88.0 88.1 

Age of Child on Second Test 

12-4 or older 37 89.7 89.3 

Under 12-4 37 92.8 98.0 

Although the average gains are small, the consistency of 

"th^gf^e^ sigmEcance.^'" '" 

Group II, the sibling group was composed of 125 pairs 
of siblings, each adopted into a different foster home and 
separated for a period of 4 to 13 years. The average age 
at which the siblings became separated was 5 years- 

1 A gain of 2.5 =*= .8, or over three times as large as its P.E, 
2 Freeman points out, furthermore, that the actual gains are somewhat larger 
than appears from these figures, since Stanford-Binet LQ.'s show a slight drop 
with age owing to certain peculiarities of the test itself. He estimates that 5 
points should be added to these gains in I.Q. in order to obtain a more correct 


4 months. The I.Q.'s of these siblings correlated only .25, 
in contrast to the correlation of about .50 ordinarily 
found between siblings reared in the same home (cf. 
Ch. IV). The scores of 63 siblings adopted into homes 
receiving significantly different cultural ratings correlated 
only .19; those of siblings adopted into similar homes 
correlated .30. These results are particularly striking 
when it is recalled that the siblings had lived together 
during the important years of early childhood. 

The third group included all foster siblings, i.e., two 
unrelated children living in the same home. This, In 
turn, was subdivided into a group of 40 pairs consisting of 
a foster child and an own child of the foster parents, and 
a group of 72 pairs of unrelated foster children. In the 
former, a correlation of .34 was found between I.Q.'s of 
the two children in^each pair; in the latter, the correlation 
was .37. These correlations are actually higher than those 
between true siblings adopted into different foster homes. 

Finally, all of the children were included in one com- 
posite group of 401 cases. This composite, labeled the 
home group by Freeman, was employed chiefly in making 
general comparisons between foster child's intelligence 
and social adjustment, and such factors as foster parents' 
intelligence and cultural level of the foster home. ^In 
th^H,tke-. group, a correlation, ol .48^ was ..found , between ' 
child's I.Q. and cultural rating of the foster^home. The 
correlation of child's I.Q. with Otis score of the foster 
father was .37 (N = 1 80) and with that of the foster 
mother .28 (N 255). These and other similar correla- 
tions again suggested the relatively large influence of 
environment upon intelligence test performance. 1 

1 The specific results cited in the above discussion are all based on the Stan- 
ford-Binet and the Otis tests. The International and the vocabulary tests 
yielded very similar results in all cases in which they were employed. 


The analyses carried out in the four groups yield results 
which corroborate each other closely. The data appear 
very conclusive. A difficulty in the way of a clear-cut 
interpretation is, however, the presence of a possible 
selective factor in adoption. Thus the more intelligent 
persons, with more cultured homes, may tend to adopt 
the more intelligent children. This would produce an 
entirely spurious correlation between intelligence of foster 
parents and children as well as between cultural level of 
the home and child's I.Q. Freeman recognizes this diffi- 
culty, but attempts to show that such selection is very 
insignificant. An examination of the application blanks 
submitted by the foster parents showed that factors 
other than intelligence were usually considered. Health, 
sex, race, and physical appearance were more often speci- 
fied than intellectual level. When the latter was men- 
tioned, it was only to require that the child be of "normal" 
intelligence, but no more specific account was taken of 
degree of intelligence. This request, furthermore, was 
made equally often by people who were themselves in- 
tellectually inferior as by those who were superior. Fi- 
nally, in over 80% of the cases, very little information 
was available at the time of adoption about the intelli- 
gence of the child or of his natural parents. In the case 
of the 74 children for whom I.Q.'s were available before 
adoption (cf. above), there is evidence that such I.Q.'s 
were employed in placing the children, "but this group 
constituted only a small portion of the total group 0/401 cases. 

If the studies of Burks, Leahy, and Freeman are evalu- 
ated together, it appears that the role of environment in 
the development of intelligence cannot be dismissed. 
Beyond this, however, it is impossible to generalize be- 
cause of special difficulties inherent in each study. In 
Freeman's investigation, the factor of selection may have 


operated, although Freeman asserts that Its effect was 
probably negligible. In Burks' and Leahy's studies, in 
which the age of adoption was much lower and selective 
factors were thus more completely eliminated, the only 
comparisons made were not very conclusive. As has 
already been pointed out, the evaluation of the foster 
data in terms of the control data was not perfectly justifi- 
able, since the parent-child relationships were probably 
dissimilar in the two groups. It is unfortunate that Burks' 
and Leahy's groups of foster children, with their obvious 
advantage of lower adoption age, could not have been 
submitted to the same varied analyses employed by 
Freeman. A comparison of siblings adopted under the 
age of one year into different foster homes, for example, 
would have been very valuable. It would have been 
quite difficult, however, to find a sufficiently large number 
of such siblings meeting the required specification in 
respect to adoption age. If one requirement is met, 
another must be sacrificed. It would seem, then, that the 
study of foster children has not yet proved as fruitful an 
approach to the problem of heredity and environment as 
it had promised to be. 


1. Burks, B. S. "The Relative Influence of Nature and Nur- 
ture upon Mental Development; a Comparative Study of 
Foster Parent-Foster Child Resemblance and True Parent- 
True Child Resemblance/ 5 2jth Yearbook, Nat. Soc. Stud, 
Educ., 1928, Part I, 219-316. 

2. Freeman, F. N., Holzinger, K. J., and Mitchell, B. C. "The 
Influence of Environment on the Intelligence, School 
Achievement, and Conduct of Foster Children," 2?th Year- 
book, Nat. Soc. Stud. Educ., 1928, Part I, 103-217. 

3. Galton, F. Inquiries into Human Faculty and Its Develop- 
ment. London: Macmillan, 1883. Pp. 387. 


4. Hirsch, N. D. M. Twins: Heredity and Environment. Cam- 
bridge: Harvard Univ. Press, 1930. Pp. 158. 

5. Lauterbach, C. E. "Studies in Twin Resemblance," Ge- 
netics , 1925, 10, 525-568. 

6. Leahy, A. M. "Nature-Nurture and Intelligence," Genet. 
Psychol. Mon., 1935, 17, 236-308. 

7. McNemar, Q. "Twin Resemblances in Motor Skills, and 
the Effect of Practice Thereon/' /. Genet. Psychol., 1933, 
42, 70-99. 

8. Merriman, C. "The Intellectual Resemblance of Twins," 
Psychol. Hon., 1924, 33, No. 5. Pp. 58. 

9. Muller, H. J. "Mental Traits and Heredity," /. Hered., 

10. Newman, H. H. The Biology of Twins. Chicago: Univ. 

Chicago Press, 1917. Pp. 185. 
IIt - . The Physiology of Twinning. Chicago: Univ. Chicago 

Press, 1923. Pp. 230. 

12 . - . "The Effects of Hereditary and Environmental Dif- 
ferences upon Human Personality as Revealed by Studies 
of Twins," Amer. Naturalist, 1933, 67, 193-205. 

13. Tallman, G. G. "A Comparative Study of Identical and 
Non-Identical Twins with Respect to Intelligence Resem- 
blances," 27th Yearbook, Nat. Soc. Stud. Educ., 1928, Part I, 

4. Thorndike, E. L. "Measurement of Twins," Arch. Psychol., 
1905,1. Pp.6^ 


A distinction has frequently been made between de- 
velopment through specific practice or training in a given 
activity and development through maturation or growth. 
Such a distinction does not imply a dichotomy between 
inherited and acquired behavior. Thus maturation is not 
regarded as independent of environmental stimulation of 
a general sort, nor is learning necessarily considered to be 
exclusively determined by environmental factors. When 
we speak of growth, we usually think of a definite se- 
quence of developmental stages in the structural char- 
acteristics of the individual. As the child grows older, 
for example, his height increases, his bodily proportions 
are altered, and many other well-known physical modifi- 
cations occur. Such changes take place regardless of the 
specific training which the individual may have had. 

As structures become altered with age, so we may expect 
their functions to undergo change. With stronger muscles, 
the older child can learn to walk, climb stairs, sit up, and 
perform various other tasks much more readily than his 
younger brother. It is logical to expect that certain 
types of activity will in general appear at fairly definite 
stages, since they require a specific degree of structural 
development for their execution. Very intensive training 
at an earlier age may produce almost negligible effects 
when compared to the achievements of an older child 
with only a minimum of training. 

Since such a large share of infant behavior consists in the 
acquisition of motor skills and sensori-motor coordinations, 



activities which are closely linked to structural factors, 
growth rather than practice seems to play the major part 
in early behavioral development. It is quite a different 
matter, however, to use the concept of growth to describe 
the intellectual and emotional development of the older 
child. Such a concept has nevertheless been commonly 
employed in interpreting age changes in mental test per- 
formance, and the curves plotted to portray these changes 
graphically have been labeled " mental growth curves." 
Such growth curves are difficult to interpret for many 
reasons and their use has led to much technical controversy. 

An equally confused issue centers about the question 
of the effect of growth or practice upon the extent of 
individual differences. Do people differ more among 
themselves ,when their general level of performance is 
high of when it is low? Will subjects become more alike 
or more unlike with training? Is variability greater among 
older or among younger individuals? In all of these 
phases of the problem of training and growth in relation 
to individual differences, there have appeared numerous 
investigations. But the results are very inconclusive and 
frequently misleading. 

In the present chapter will be discussed those investiga- 
tions which are primarily concerned with the effects of 
specific training upon performance. In such studies, some 
effort is made to bring about a change in behavior under 
experimentally controlled conditions. Those investigations 
which simply present observations or measurements made 
on different age groups without any attempt to alter the 
course of development will be given in the following chapter. 


In the course of extensive and carefully controlled ob- 
servations and experiments conducted at the Yale Psycho- 


Clinic, Gesell * has established developmental norms of 
infant behavior for different ages. Since the behavior 
repertory of the child during the first few years of life 
consists so largely in the exercise of simple sensory and 
motor functions, most of the data are drawn from this 
type of activity. Gesell concludes from various findings 
that such activities depend chiefly upon growth or matura- 
tional factors. Among his evidence he cites observations 
on pre-term and post-term babies. Infants born pre- 
maturely, before the normal nine-month gestation period, 
do not reach the developmental level of the normal new- 
born child until the age of one month. Similarly, a baby 
born after a ten-month gestation period will be as far 
advanced in its behavior at birth as a normal one-month 
old child. Yet the differences in opportunity for specific 
practice in prenatal and postnatal environment are ob- 
viously large. 

Qesell likewise points to the consistency of develop- 
mental sequences, as evidence for maturation. In the 
development of prehension behavior, for example, the 
successive stages come in the same order and at approx- 
imately the same ages in different children. Observation 
of the child's reactions towards a small sugar pellet showed 
that both in visual fixation and in hand and finger move- 
ments, characteristic behavior was displayed at successive 

Training experiments also tended to corroborate the 
same general view. A series of experiments were con- 
ducted by the "method of co-twin cpntrpl" whereby one 
member of a pair of identical twins is subjected to inten- 
sive training in some activity while the other is used as a 
control subject and prevented from exercising the func- 
tion under investigation. In one such experiment (7, 

1 Cf., e.g., 6 and 7. 


p. 654), stair-climbing and "cube behavior" (including 
prehension, manipulation, and constructive play with 
cubes) were studied on a pair of identical female twins, 
46 weeks old at the beginning of the experiment. The 
trained twin (T) was put through a daily 2ominute 
training period in both types of activity for six weeks. 
At the end of this period, the control twin (C) who had 
had no specific training in these functions proved equal 
to T in cube behavior. In stair-climbing, a difference 
was found. Whereas T was a relatively expert climber, 
her sister could not reach the top of a five-tread staircase 
even ^ith assistance. Two weeks later, however, still 
without any previous training, the control twin was able 
to climb to the top unassisted. At this age (53 weeks), 
twin C was herself given a two-week training period, at 
the end of which she approximated T in her climbing 
skill. Thus, because of the higher level of maturational 
development, a two-week training period at 53 weeks of 
age proved to be nearly as effective as a six-week training 
period at 46 weeks. 

Experiments on intensive training in infancy have also 
been conducted by McGraw (10). A pair of male twins 1 
were observed from birth to the age of 22 months. Jimmy, 
the twin who appeared stronger and better developed at 
birth, served as the control, his activity being approxi- 
mately that of a normal infant during the earlier period 
and possibly a little more restricted than normal later. 
The other twin, Johnny, was put through intensive daily 
training from the age of 20 days. Both twins lived at 
home but were in the laboratory between 9 and 5 o'clock 
for five days a week. The performance of the trained 
twin in each task was compared throughout the period 

1 Originally believed to be identical although subsequent physical character- 
istics threw doubt upon this designation. 


of the experiment with that of the untrained control twin. 

Specific exercise was found to have little or no effect 
upon a group of activities including simple reflexes, such 
as suspension-grasping, as well as crawling and creeping, 
erect walking, sitting, prehension, and others. Marked 
improvement resulted, however, from practice on a group 
of somewhat more complex functions such as skating, 
jumping, swimming, diving, ascending and descending 
inclines, getting off stools, and manipulating and climbing 
stools and boxes to reach an objective. Although a certain 
amount of sensory and muscular development obviously 
helps in the latter functions, their performance seems to 
depend largely on specific training. The independence 
of the former group of functions from practice confirms 
many of GeselFs findings. For the execution of these 
simpler functions, the presence of structures of a certain 
degree of development seems to be sufficient or nearly 

In an experiment by Dennis (4), the opposite procedure 
of restricting training was followed. Two female infants, 
who happened to'be fraternal twins although this was not 
essential to the present experiment, were reared in the 
experimenter's home under controlled conditions from 
one to 14 months of age. During this period, all oppor- 
tunity to stand or sit was "eliminated and opportunities 
to grasp objects were reduced to a minimum. Comparing 
the behavior of these infants at successive periods of the 
experiment with norms established by Gesell and others, 
Dennis found marked retardation in these functions. The 
infants Wre unable to stand, sit unsupported, or grasp 
a dangling ring at the ages reported as "normal" for each 

These experiments indicate some of the major trends 
revealed by the study of infant behavior. There are some 


activities which depend so largely upon structural condi- 
tions, such as sensory, muscular, or neural development, 
that their performance is almost completely unaffected 
by specific exercise. When more complex and less struc- 
turally fixed activities are investigated, however, the effect 
olLtraining is apparent. It should also be borne in mind 
in interpreting the above experiments that conditions 
were never perfectly controlled. For practical reasons, it 
is impossible either to determine or to observe all the 
stimulation to which the infant is exposed. In McGraw's 
study, for example, no control was exerted over the in- 
fants' activities during the time they spent at home. 
Finally, even if specific practice is rigidly prevented, the 
influence of the more or less random and general training 
which the infant obtains in the course of everyday activity 
cannot be ignored. Thus, for example, the greater effec- 
tiveness of training in stair-climbing when applied at a 
later age may result as much from the fact that the older 
child has used his muscles more in various general activ- 
ities, as from his more advanced age. 

Mention should also be made of experiments on infra- 
human organisms, both by the method of special training 
and that of restricted practice. In their general implica- 
tions, the findings are very similar to those on human 
infants. Certain functions, such as the flying of birds (13) 
or the swimming movements of tadpoles (2), for example, 
have been found to depend almost exclusively upon struc- 
tural development. Other activities require a moderate 
amount of specific exercise together with a certain level 
of physical development for their normal execution; still 
others depend very largely upon the nature of the train- 
ing and specific stimulation to which the organism is 
subjected, and are affected only in a very general way 
by maturational factors. 



Attempts have also been made to investigate the effect 
of specific training upon functions, such as memory or 
intelligence test performance, which are more complex 
and less directly related to sensori-motor development. 
Most of these experiments have been conducted on chil- 
dren of elementary school age. Gates (5) studied the 
effect of continued practice upon memory span for digit. 
Two groups of schoolchildren, selected so as to be equiv- 
alent in age, number of boys and girls, Stanford-Binet I.Q., 
school grade, teachers' estimates of scholastic maturity, 
and scores on several memory tests, were given an initial 
test in digit span. The children in the Practice group 
were then put through individual practice in recalling 
digits on each of 78 days extending over a period of five 
months. At the end of this period, both Practice and 
Control groups were given a final test. The average 
scores on initial and final tests are reproduced in Table IV. 


(After Gates, 5, pp. 454~456) 


Initial Test 

Final Test 

After a Lapse 
of 4% Months 

After Common 
Practice for 
22 Days 







^ Jbut^the ^Practice group 

is clearly ahead, manifesting a ^ia.whick.aozmji re- 

a six-year period, according to the Stanford-Binet 
norms for this function. Four and one-half months after 
the SnaTtes^5oSL groups were again tested, by a differ- 


ent examiner. This time the Practice and Control groups 
were approximately equal Finally, the two groups were 
subjected to 22 days of practice, at the end of which both 
showed improvement and in approximately equal degree. 
It was also found that the training in digit span had no 
effect on performance in other types of mental tests. 

From these findings, Gates concludes that training is 
highly specific, consisting in the acquisition of special 
skills and techniques, and that it does not alter the 
growth of the underlying mental functions. It is unfor- 
tunate that in most studies on experimentally adminis- 
tered practice, all effects not directly resulting from such 
practice are attributed indiscriminately to growth or mat- 
urational phenomena, the influence of the vast amount 
of other training which the child is receiving in the course 
of everyday life being disregarded. 

In Gates' experiment, the fact that the Control group 
also improved, although to a lesser extent than the Prac- 
tice group, suggests the effect of other intervening experi- 
ences rather than growth. This explanation is further 
corroborated by the finding that both groups drop to an 
equal level when retested later by another examiner. The 
drop may have resulted from the time of year at which 
the tests were administered, or from other factors inci- 
dental to the school situation. The closeness with which 
the child attends to the material and the effort he puts 
forth to concentrate on the task of memorizing are very 
important factors in determining his span; and it seems 
entirely plausible that such factors should be affected 
both by the attitude of the particular examiners and by 
the sum total of school experiences which the child has 
had. It is noteworthy that the 4|-month period preceding 
the drop in score included the summer vacation, which is 
definitely an environmental and not a maturational inci- 


dent. The marked susceptibility of a, function like memory 
span to. training, which this experiment demonstrated, 
seems in itself to minimize maturational factors. To as- 
sume the existence of some underlying hypothetical capac- 
ity of memorizing which remains unaltered while per- 
formance on a memory span test rises and falls seems 
totally unwarranted by the facts and not a very clarifying 
procedure in any event. 

Several investigations have been conducted to deter- 
mine the effect of special training or coaching upon 
Stanford-Binet scores. In three studies (3) carried out 
under the direction of Terman at Stanford University, 
children were given instruction and practice for several 
weeks on material either identical or similar to some of 
the tests in the Stanford-Binet scale. The groups were 
small, varying from 10 to 26, but in each study the trained 
group was carefully matched with a control group by 
"pairing" the subjects. All experiments clearly demon- 
strated the possibility of teaching a child to perform 
tests which he was formerly incapable of doing because of 
age or mental level. The influence of this improvement 
upon the LQ. obtained on the whole scale differed in the^ 
three studies, being most evident, as would be expected, 
in that study l in which the trained" functions overlapped 
with the largest number of Stanford-Binet tests. In this 
st^dy, furthermore, retests after a six-week period, during^ 
whicH lieitKef group had received any trajjung, jshpwfc&the 
practice group to have retained its advantage over the 
control group. 

WYCS.tigatiQix on the .effects,, of, coaching 
is reported by Greene (8). Three groups of children were 
given the Stanford-Binet. The subjects in one of these 
groups were then coached on the specific tests in which 

1 I.e., the study by Casey (3, pp. 431-433). 


they had failed. A second group was coached on material 
similar but not identical to that in the Stanford-Binet. 
No child in either group was coached for over two hours 
altogether. The third group served as a control, receiving 
no special training in the test material. All groups were 
retested at intervals of three weeks, three months, one 
year, and three years after the initial tests. The average 
I.Q.'s of each group on the initial test and each of the 
four retests are given below (8, p. 425). The results 
obtained in two schools, A and Y, have been kept sep- 
arate since a slightly different method of coaching was 
employed in each. 

School A School Y 

Test Control Coached Similar Control Coached Similar 

(N = 9) (N = 1 8) (N = 17) (N = 17) (N = 11) (N 16) 











3 weeks 









3 mos. 









I year 









3 years 





1 02 



It will be noted that whereas the control groups show 
only irregular fluctuations from time to time, the coached 
groups in both schools undergo a marked improvement 
oji the second test which followed shortly after the coach- 
ing period. This improvement is retained on successive 
retests, although in ever decreasing amount. The grad- 
ual drop in I.Q. observed in the coached groups may be 
owing partly to forgetting of the coached material and 
partly to the fact that, as the children grew older, they 
were tested to an increasing extent at higher age levels 
in which they had not been coached. That the latter is prob- 
ably the major factor is demonstrated by a comparison 
of the coached groups in the two schools. In school A, 
the children were coached more intensively on fewer 
tests; in school Y, they were coached on two additional 


higher levels. Thus the effects of coaching in school Y 
should not be "outgrown" as readily as in A. The aver- 
age I.Q.'s do in fact show that the dropping off does not 
occur as rapidly in Y as in A. The groups trained on 
similar material also show an immediate improvement 
which gradually disappears on successive retests. As 
would be expected, the gains in these groups are much 
smaller throughout than in the groups which had been 
directly coached. 

All of these studies indicate the very great extent to 
wElcE""l]aeatal test performance may be influenced by 
training. Such findings suggest vast possibilities regarding 
the part played by the incidental and often accidental 
training of everyday life. That, the effects, of a brief 
period of training are not permanent seems to be quite 
beside the point. When training is discontinued, we should 
naturally expect the improvement to fall off because of 
forgetting. If, furthermore, children are tested in different 
functions at successive ages, as they are to a large extent 
in the Stanford-Binet, the effects of training will not be 
manifested over a long period. It is futile to expect that 
a brief period of highly specific instruction or practice 
should raise the "general mental level" of the child, 
especially since such a mental level is itself a manifold 
of widely diverse and loosely interrelated functions. Train- 
ing does have a very real effect, however, upon the indi- 
vidual's performance on specific mental tests. And this 
is of prime importance since all our observations regarding 
the subject's psychological make-up are ultimately derived 
from such concrete behavior. 


about a pronounced change in giej^l test, performance, a 


further question may be raised regarding the differential 
effects of such training upon individual subjects. Will 
the^ initially better individuals benefit more than Tfie 
initially poorer? Will subjects tend to maintain the same 
relative standing in the course of training? .E&Jndjyidual 
differences increase or decrease with practice? If these 
questions are still unanswered, it is not for dearth of data, 
for they have been repeatedly investigated with a wide 
variety of materials, methods, and subjects. 1 The entire 
problem is so beset with technical difficulties, however, 
as to have even been declared insoluble by some. The 
crux of the matter is that entirely opposite conclusions 
can be drawn if the results are expressed in different 
forms, a fact which has cast an aura of artificiality over 
all the data. 

In the present section will be given a brief survey of the 
major issues involved in the problem of practice and vari- 
ability. These must be considered before any attempts 
are made to examine the particular findings. The data 
are meaningless unless evaluated in terms of the specific 
questions which we wish to answer and the methodology 
necessitated by such questions. This section may seem 
somewhat of a technical digression, but it cannot be 
eliminated from any analysis of the effects of practice 
upon individual differences. Attempts to present only a - 
simplified summary of results have proved exceedingly 
misleading, since the reviewer in such cases must either 
arbitrarily omit many of the data or offer conflicting 
conclusions with no possibility of reconciling them. 

, 2! A J^lffipwlti^ Q -this, probkni, are,, inherent in 
arison of yan.ability^jsither ^ from,, trait , tpjjait 
(cf . Ch. II) ^or from one condition to another^ As is true 

x For summaries of the relevant literature, the reader is referred to Kin- 
caid (9), Peterson and Barlow (n), Reed (12), and Anastasi (i). 


in all of these cases, if a solution is to be found it must 
be stated in terms of a specifically defined situation. 
Much of the controversy and confusion seems to have 
arisen from the attempt to go beyond the concretely 
established facts and discuss a sort of disembodied ab- 
stract " variability " which is expected to be independent 
of the particular situation in which it has been measured. 
In any analysis of the effect of practice upon individual 
differences, it is necessary to ascertain at the outset wjiat 
is meant by equal practice. If all in^mduals,^re,peimit,ted 
to practice for ^13. equal period of time, the slower .worker 
will be at a disadvantage since he will have received 
practice on less material than the faster individual. The 

**.."..,..,,.. ; , ' , ", ***, 

use of an equal amount ,pf , rriaterial, on the other hand, 
places a handicap on the faster worker who will neces- 
sarily spend less time in training than the slower perspn. 
Tljie amount /zwi^methodj^iying the^ advantage to . v the^ 
initially poorer individual, fayors a decrease in .variability 
with practice, whereas the time limit method favors,,, an 

Each method answers a somewhat different question. 
The best criterion for choosing between the two seems 
to be a practical one. Equal training, as the term is 
used in everyday life, usually refers to equal time spent 
in training. When a person takes a "course" in music, 
or golf, or Spanish conversation, he is given a specified 
number of lessons, each of the same duration. No adjust- 
ment is made for the fact that during that period the 
number of times a piano key is touched or a golf ball is 
hit, or the number of words spoken differs widely from 
one individual to another. 

I* 1 Table V are 
illustrated three alternative ways of reporting the same 



I. Amount Scores 



Number of Items Completed 
during a i-Minute Trial 

Gain in Items 
-per Trial 



First trial 

Last trial 





2. Time Scores 



Average Time in Seconds 
to Complete One Item 

Gain in Time 
per Item 



First trial 

Last trial 



3 . Time Saved p er 



Gain in Items 
per Trial 


Time Initially 
Each Item 

Gain in Time 
per Trial 


scores obtained by two subjects, A and B, with the time 
limit method. In this table, A represents an initially faster 
worker and B an initially slower one. It will be noted 
that the relation between the gains of the initially better 
and poorer subjects differs in each method. When the 
scores are expressed as amount of work done per unit of 
time, the gain of the better subject appears larger than 
that of the poorer one. This will tend to make variability 
increase with practice. If, on the other hand, these same 
scores are expressed as time per unit of work, the slower 
individual will seem to gain more. 

This apparent contradiction becomes intelligible if we 
realize just what time and amount scores are^nxqasuring. 


for ^ every additional item which he completes within^ the 


given period after practice he will be saving much more time, 
than^ the faster worker. Thus, if It took the slow worker B 
5 seconds to complete one item at the beginning of prac- 
tice and if he can complete 8 more items after practice 
than he could before, he has gained the equivalent of 
8 X 5 or 40 seconds per trial The faster worker A 3 on 
the other hand, added 10 items to his score, but he only 
required 3 seconds per item at the outset, so he has gained 
10 X 3 or 30 seconds (cf. method 3, Table V). The gain 
in time per item (method 2, Table V) favors the slower 
worker even further, since it does not take into account 
the fact that during any one trial this unit gain in speed 
is manifested more often by the faster than by the slower 
worker, the former completing more items. 

It is apparent, then, that the problem of practice and 
variability must be further defined in terms of the measujre 
of '-progress employed. , If a choice is to be made among 
the various measures, amount scores will prove more 
serviceable because of their wider applicability. In a 
"speed" test, amount scores can be employed inter- 
changeably with time scores. In a "power" test, however, 
in which the items are arranged in an order of progres- 
sively increasing difficulty, a time score would be meaning- 
less. If, for example, in a 3O-minute test consisting of 
10 problems, all the subjects attempt all the problems 
but the number of correct solutions ranges from I to 10, 
it would be absurd to report that the average time per 
problem ranged from 30 minutes to 3 minutes. The better 
subjects worked no faster than the poorer subjects since 
all members of the group tackled all the problems. 

' the scores have been found, there 
irmmmt, a Jfe . data. A jivefy 

. goiug on regarding tfee use of rela- 
tive or absolute pleasures of variability in practice ex- 


periments. When^absplute measures are used, such as the 
standard deviation^ or gross gains made by Initially high 
and low individuals or groups, variability tends to increase 
with practice. When, on the other hand, relative measures 
are employed, such as the coefficient of relative variabil- 
ity, 1 or some measure based upon relative or percentage 
gains, then variability decreases with practice in most 
cases. The fundamental objection against the use of 
relative measures has already been discussed in a previous 
chapter (cf. Ch. II). It was there demonstrated that, 
sig.ce scores on most current psychological tests are not 
measured from an absolute zero point of performance, 
any ratios or quotients computed with such scores may 
be entirely misleading; the addition of a few easy items 
at,,,the .lower end of the scale might completely, reverse 
the relationship between the obtained values. 

Thus it would seem that absolute measures of variabil- 
ity are preferable for a purely negative reason, if for no 
other. Since relative measures are ruled out by the use 
of arbitrary starting points in the tests, no alternative 
is left. We may, however, inquire more directly into the 
logic of using absolute or relative measures in practice 
experiments. Tjh^e argyineatiii, support of relative, meas- 
ures is that, since the numerical size of scores changes 
Ln,tb&.0ur$? pi, practice,, the scqres, ai-e ixo.t. expressed in 
the same units throughout 4&d ,heace,ab?plute,,measures 
will not be comparable from r tr;i^l T tQ y tnal. Through chance 
alone^, the, argument runs, absolute variability, will, mc%2ase 
wJiea- the^sizfiMjoL^ jwhen the 

scores decrease, such changes, being therefore of the nature 
of a statistical artifact. 

It is perfectly true that, other things being - equal, 

1 iooS.D. 


numerically larger scores will exhibit greater variability. 
Obviously, if the standard deviation o a distribution 
of time scores is 10 minutes, the standard deviation of the 
same scores expressed in seconds will be 600. For the 
same reason, the standard deviation of the number of A's 
cancelled in one minute cannot be compared directly 
with that of the number of additions performed during an 
equal period, since the latter scores would be much smaller. 1 
This type of argument does not necessarily hold, how- 
ever, when the same test is given to different groups or 
to the same group under different conditions, such as 
before and after practice. Let us suppose that the average 
score of a certain group I on an intelligence test is 25 points 
and that of group II 50 points. It does not necessarily 
follow from this difference in averages that group II 
will have a larger standard deviation than group I. In 
fact, the opposite might very likely be the case. If 
group I, for example, consisted of unselected third grade 
public school children and group II of superior sixth 
grade children in a private school, the latter would prob- 
ably have a lower standard deviation. Similarly, one could 
assemble without too much difficulty two groups of men, 
whose average heights were 64 and 72 inches respectively, 
but whose standard deviation was 8 in both cases. It 
would be quite absurd to insist that the taller group is 
"actually" less variable in height than the shorter, or to 
suggest that the inches used in measuring height had in 
some mysterious fashion changed in value from group I 

to group II. I\J52HlfLjS2Hi . ^at ^ ,?9 m P ar J s !P.J2f 
variability before and after practice is more similar in 

pr^iplt'to t^tjsibov^ examples tj^fl to jthe raeasuWTOSPt 
of variability in diffe^nt te,^^, Tlie, ,jz, of absolute 
measures in this connection is therefore^stifiable. 

1 Cf. Ch. II for a fuller discussion. 




If the problem be formulated in specific terms, we can 
legitimately inquire into the effects of practice upon mdi- 
vidual differences. For reasons of convenience, as discussed 
above, we "may arbitrarily define equal practice as equal 
time spent in practice and express scores in terms of 
amount done per unit time. Variability is to be measured 
in absolute terms, for the reasons stated in the preceding 



(After Anastasi, I, pp. 40-42) 





Hidden Words 



















































































































































































1 The scores on all of these tests were transmuted into an equal unit scale and 
are thus directly comparable from one test to the other. 


paragraph. Under these conditions, the findings of differ- 
ent experimenters agree very closely. An investigation 
by Anastasi (i) illustrates the general methods and find- 
ings of such studies. 

Four groups, each comprising from 114 to 200 college 
students, were given continuous practice in one of four 
tests. The tests included A~Cancellation, Hidden Words, 1 
Symbol-Digit Code Learning, and Vocabulary Learning. 2 
The practice consisted of 15 4-minute trials in Hidden 
Words and 20 2-minute trials in each of the other tests, 
a different group of subjects being employed for each 
test. The average scores and standard deviations of the 
scores on each trial are reproduced in Table VI. 

It will be readily seen that, the standard deviation^ rise 
with practice in, every test. It was also found that indi- 
viduals tend to maintain the same relative,, staading in 
the group in the course of practice, the correlations be- 
tween initial and final scores of the same, sahjecta. being 
consistently positive and usually high. For the four tests, 
these correlations were: 

Cancellation .6725 

Symbol-Digit .2981 

Vocabulary -S73 

Hidden Words .8239 

Such correlations indicate a tendency for the individual 
who is best in the group at the outset to remain at the 
top after practice, for the one who is lowest to remain 
at the bottom, and so on. This is commonly found to be 
the case in all experiments on practice. 

Both the tendency to maintain the same relative posi- 
tion during practice and the increase in absolute variabil- 

1 Subjects were to underline all four-letter English words which were "hidden" 
in a page of pied type. 

2 Subjects learned, by the method of paired associates, a "vocabulary" of 
nonsense syllables; the test is similar to code learning, but more difficult. 



ity are illustrated graphically in Figure 25. This shows the 
learning curves of two subjects on the Hidden Words 
test. The subjects were selected near the extremes of the 
distribution, the differences between their initial scores 

95 r- 



I 70 

I 65 

I 60 


a! 55 







I I 

I I 




-I 95 



10 11 12 13 14 15 

WITH PRACTICE. (Unpubl. data from, investigation of Anastasi, I.) 

being very large. It will be noted that the curves do not 
at any time cross and that they diverge with practice, 
the differences between the two individuals being much 
larger on the fifteenth trial than they were on the first. 
Itjias ^be^ii, frequently assumed- that ifJiidisdduaLdiffer- 
s Jua performance incuase with practice, , J:Jxc^jCja,, be 

to hereditary differ,erj,ce$^ wh 
se^ .they inust have t resulted^ in , J^ 


from inequalities of past training and environmental stim-^ 
ufation. It is^argued that .when subjects undergo a, pro- 
longed period of equal training, the differences in their 
past experience with the given task are thereby wiped out. 
This assertion is open to question. The influence of en- 
vironmental factors upon the development of the indi- 
vidual is ordinarily cumulative. If one individual's past 
experience has made him more proficient than another 
in a certain task, we should expect him to be better fitted 
to profit from instruction for that very reason. Suscepti- 
bility to training can itself be environmentally deter- 
mined, and if so determined there is no reason to assume 
that it will disappear with additional training. The indi- 
vidual who has been handicapped by a poor environment 
may lack the necessary intellectual tools to profit from 
instruction. Thus, had the Wild Boy of Aveyron (cf. 
Ch. Ill) and a boy of the same age from a middle class 
English home been put through an identical one-year 
course in the reading of French, the differences in their 
abilities to read that language would have been far greater 
at the end of the course than at the beginning. , It i$ 
obviously unnecessary to assume an hereditary basis^of 
individual differences in order to account for the increase 
in variability in such an^, example. The more the indi- 
vidual has learned in the past, the more he will be able 
to learn in the present. To use a rather crude analogy, 
we might say that practice does not add to the individual's 
ability, but multiplies it. 


1. Anastasi, A. "Practice and Variability: a Study in Psycho- 
logical Method/' Psychol. Man., 1934, 45. Pp. 55. 

2. Carmichael, L. "A Further Experimental Study of the 
Development of Behavior," Psychol. Rev., 1928, 35, 253-260, 


3. Casey, M. L., Davidson, H. P., and Harter, D. I. "Three 
Studies on the Effect of Training in Similar and Identical 
Material upon Stanford-Binet Test Scores," 2jth Yearbook, 
Nat. Soc. Stud. Educ,, 1928, Part I, 431-439. 

4. Dennis, W. "The Effect of Restricted Practice upon the 
Reaching, Sitting, and Standing of Two Infants," /. Genet. 
PsychoL, 1935, 47, 17-32. 

5. Gates, A. I. "The Nature and Limit of Improvement Due 
to Training," 27th Yearbook,, Nat. Soc. Stud. Educ., 1928, 
Part I, 441-460. 

6. Gesell, A. Infancy and Human Growth. N. Y.: Macmillan, 
1928. Pp. 418. 

7. . "The Individual in Infancy." Ch. 16 in The Foun- 
dations of Experimental Psychology, C. Murchison, ed. 
Worcester: Clark Univ. Press, 1929. Pp. 907. 

8. Greene, K. B. "The Influence of Specialized Training on 
Tests of General Intelligence," 27th Yearbook, Nat. Soc. 
Stud. Educ., 1928, Part I, 421-428. 

9. Kincaid, M. "A Study of Individual Differences in Learn- 
ing," Psychol. Rev., 1925, 32, 34-53. 

10. McGraw, M. B. Growth: a Study of Johnny and Jimmy, 
N. Y.: Appleton-Century, 1935. Pp. 319. 

11. Peterson, J., and Barlow, M. C. "The Effects of Practice on 
Individual Differences," 27th Yearbook, Nat. Soc. Stud. 
Educ., 1928, Part II, 211-230. 

12. Reed, H. B. "The Influence of Training on Changes in 
Variability in Achievement," Psychol. Mon., 1931, 41. 

PP. 59. 

13. Spalding, D. A. "Instinct: with Original Observations on 
Young Animals," Pop. Sci. Mo., 1902, 61, 126-142. 


e subsec l ue ntly shown, the distinction between 
investigations of training and those of mental growth is a 
superficial one. It is only for convenience, therefore, that 
the former were discussed in the preceding chapter, while 
the latter will be surveyed in the present one. The data 
of the two chapters should be considered as a whole. A 
few studies are difficult to classify into one or the other 
category; this is especially true of experiments on very 
young children, such as those reported in Chapter VI. 
For the purposes of the present discussion, however, we 
may regard studies of "growth" as those in which mental 
progress at successive ages is observed and charted, with 
no attempt to alter the normal course of development. 


Growth curves were first plotted to show the develop- 
ment of physical traits, such as height, weight, bodily 
proportions as indicated by various indices, and the like. 
An example of such a curve, showing the changes in height 
in groups of tall, average, and short girls between the 
ages of 5 and 17, is given in Figure 26. As a descriptive 
technique for portraying more vividly the course of de- 
velopment of structural characteristics, the growth curve 
has proved serviceable and Intelligible. The physical 
data are relatively easy to interpret and unambiguous. 


es pf "mental gjpwtji," a 
additional confusion into an already difficult problem 




At^best these curves are only a descriptive summary of 
changes produced by a multiplicity of factors; by lumping 
all such factors together and giving them a semblance of 
systematic growth, the main issues are only obscured. 

Two general methods have been followed in the study 
of age changes in mental traits. The more direct ap- 


</> 150 
1 145 

1 140 



f 125 

X 120 





5 6 7 8 9 10 11 12 13 14 15 16 17 18 
Age in Years 

(After Baldwin and Stecher, i, p. 13,) 

proach is to retest a group of individuals at successive 
ages, a very laborious and time-consuming procedure. This 
method is also open to the objection that specific practice 
effects may operate in successive administrations of the 
same test or closely parallel forms. The more common 
method is to test different age groups at the. same time. 
The average score of each age group is th^n regarded as 
indicative of the normal course of development at suc- 
cessive age levels. Such a procedure is subject to serious 
selective factors, since the different age groups may not 



be comparable. An illustrative study by each method' 
will be described briefly. 

In one of the most extensive investigations of " mental 
growth,"JTeagarden (13) tested 408 subjects between the 
ages of I2 an3TT67"The standing of the group as a whole 
on intelligence tests showed them to be typical of Amer- 
ican children and adolescents, their median Stanford- 
Binet I.Q. being 93,5, with a range from 61 to 136. 
All subjects were given the Stanford-Binet, Army Alpha, 
Pressey Senior Classification 1 and Stenquist Mechanical 
Aptitude Tests. Growth curves were plotted for each test. 
Apart from many irregularities resulting from selective 
factors, as well as certain differences from test to test, 

the typ 

A compos- 
ite curve for the four tests is reproduced in Figure 27. 

65 r 

| 55 

| 45 



14 15 16 17 18 19 -20 
Chronological Age 

(After Teagarden, 13, p. 78.) 

^ in- a ^ 

differences increase3"with age, variability'being 

"" "*" ' "" " ^^" r 


Baldwin and Stecher (i) administered the Stanford- 
to^TgroupoFTt43 normal and superior children 

1 A group test of "general intelligence.' 1 . ' , 



between the ages of 5 and 14. The study differed from 
Teagarden's In many respects. The group was younger 
and included more children at the higher intellectual 



8 9 10 11 12 13 14 

Chronological Age in Years 

STANFORD-BINET MENTAL AGES. (After Baldwin and Stecher, i, p. 11.) 

levels, the LQ.Y ranging from 90 to 167. The retest 
technique was employed, each child being tested from 
two to five times within a four-year period. Growth 
curves were plotted exclusively in terms of mental ages. 


In constructing these curves, the retest data were com- 
bined with data on equivalent groups of children at 
different age levels, so that the curves are not based 
on the same subjects throughout the age range. In Fig- 
ure 28 will be found the growth curves, plotted separately 
for normal and superior boys and girls. It will be seen 
that these curves resemble straight lines very closely and 
do not exhibit the usual negative acceleration. /The 
curves of the normal and superior groups diverge with age, 
again indicating an increase in variability with age. 

The problem of the effect of age upon the extent of 
individual differences is subject to the same difficulties 
as that of practice and variability. Since most studies 
have employed amount scores, absolute variability has 
usually been found to increase with age, as it does with 
training. In the interpretation of the growth curve itself 
as a picture of the course of mental development, addi- 
tional and more serious difficulties are met. The weak- 
nesses inherent in both the retest method and the equiva- 
lent group method have already been mentioned. It is 
the latter and cruder method which has more frequently 
been followed for reasons of convenience. The choice 
of subjects also affects the type of curve obtained. When 
only younger children are tested, for example, the curve 
may resemble a straight line because it represents only 
the first part of the growth curve and is cut off before 
the negative acceleration becomes sufficiently large to be 

xpjnplex scale such as tj^e , ..SJtMlojd-Binet is 
g same abilities are not measured throughout 
the age range. ^At the ^ upper age Jevel^ 
scaLsJ^jiiu^^mpre heavily loaded ^itjb^yjgrbajj^ts. It 
has also been pointed out that the form of the curve of 
mental growth may differ with the difficulty of the test. 



In a relatively easy .task,, performance will improve rap- 
Myjdunng '"the first few years and more slowly later on 
as^a perfect score is approached. In ajrelatively difficult 
task, on the,, other -hand, or a task which requires a certain 
degree of general information or mastery of techniques 
^forefit can be properly executed, progress will be slow 
at first and much more rapid at the upper age levels. 
The latter task would thus give a positively rather than a 
negatively accelerated curve. This has been illustrated 
by Freeman (5) by means of performance curves of suc- 
cessive school grades on easy and difficult sentences in 
the Trabue Sentence Completion Scale. The curves for 
five representative sentences of different degrees of diffi- 
culty are shown in Figure 29. 

100 r 


School Grade 

OF VARYING DIFFICULTY. (After Freeman, 5, p. 336.) 



curve is to be found in the_unjt^^m w terms of which the 
cs^v^^piQ^dJ'' >> TE^'use of mental ages, as, in the study 
by Baldwin and Stecher reported above, is particularly 
misleading. It can be readily demonstrated that if aver- 
age mental age is plotted against chronological age, the 
result must be a straight line, unless the test is not suf- 
ficiently well standardized or is unsuited to the group 


upon which It was employed. To obtain a mental age 
growth curve which approximates a straight line simply 
serves to show that the test fulfills its purpose satis- 
factorily, since an age scale is constructed in such a way 
that the average child will progress one year in mental 
age during each year of life. Thus the successive mental 
age units are adjusted so as to rule out automatically any 
differences in the amount of improvement from year to 
year and are completely unsuited to an analysis of the 
course of mental development. The Jinits in which a 
growth curve isjglotted should be equal ^EroupioufTiLe 
range; otherwise they will present a completely distorted 
picture. Various statistical devices have been suggested 
in order to arrive at a "true" picture of the course of 
mental development, but these techniques are still im- 
mersed in much technical controversy. 1 

ItJsjL2arent that for many reasons the available curves 
of mental growth are of doubtful significance. Apart from 
technical difficulties, however, we^may question even the 
concept of a growth curve in the_ analysis , of mental 
development. What such .a. curve, actually . shows is the 
performance of the individual at different ages in some 

1 Thorndike (15, pp. 463-466) presents a negatively accelerated curve to in- 
dicate the general trend of development in scores on the CAVD Intelligence 
Examination, which is scaled in equal units from approximately absolute zero. 
This curve, however, represents a very rough estimate based on data from many 
widely varying groups of subjects who had taken different levels of the test. 

Thurstone (17) plotted the Stanford-Binet scores of 4208 children between 
the ages of 3 and 17, in terms of "absolute scale units," a scaling technique which 
he had devised particularly for the study of mental growth. The curve he ob- 
tained was positively accelerated at the lower age levels and negatively accelerated 
at the upper. 

Courtis (3) has suggested a unit which he calls the isochron for the measure- 
ment of growth. He defines an isochron as one one-hundredth of the total time 
required for maturation. In plotting a growth curve, he takes the developments 
made in equal intervals of the total maturation period as equal. When isochrons 
are substituted for conventional units of achievement and plotted against ago. 
a straight line is obtained as the growth curve. 


standard test situation. Such a curve does not differ 
in any essential respect from a learning curve. In both 
cases, the subject is tested under similar conditions at 
successive intervals and his progress is charted on the 
curve. Learning curves, to be sure, usually cover a shorter 
period of time than growth curves, although a practice 
experiment could conceivably extend over several years. 
The major difference between learning curves and growth 
curves seems to be that in the former the subject is given 
special training under rigidly controlled experimental con- 
ditions, while in the latter he is left to his own resources. 
Thus jjLwpuld^seem that a mental growth curve is at best 
a practice curve obtained in the absence of controlled 
conditions. 1 It reflects the cumulative effects of the ran- 
dom training and experience of everyday life, without 
adding anything essentially new to the picture. 

It follows from this discussion that growth curves are 
specific to the cultural milieu in which they are obtained. 
If the learning conditions differ from one group to an- 
other, the curves of mental growth should likewise be 
expected to differ. It might be suggested that the mental 
growth curve could still serve a useful purpose as a descrip- 
tive device. As such it would indicate the general course 
of development to be expected under given cultural con- 
ditions^ and would characterize individuals of different 
age levels within a specific group. For this purpose, how- 
ever, it seems that a more useful and intelligible picture 
could be obtained by observing cross-sections 2 of the 

1 This seems to be in general agreement with the view expressed by Courtis 
(3, 4), who regards growth as development under constant environmental condi- 
tions, and subsumes practice curves under the heading of growth curves. It 
seems to the writer, however, that the issues involved would be better clarified 
if growth curves were regarded as a type of practice curve, rather than vice 

2 Cf., e.g., the interesting descriptions of the individual at various ages given 
by Hollingworth (7). 





w Wi 

n 5 

1-3 S? O 



a w 










J ON O *^ t^oo "-o en enVO w 

M cn w ^ t^-oo MD i-o IN. M 10 u-> O^O 00 Jt>. c 


M in ^vo VOOD 

w -rh co IN 

ON ^ 

O o 


M M ^ 


O\ en 

to O 
cr> oV 

ON tn 

to c 

oo en 

u-) O 
Q ^ 


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O ONOO >-vo to ^t- en M M O a\oo t>.vo UTI ^ to c* I JJ r/ 




individual's behavior at various intervals, rather than 
tracing isolated traits through successive years. 


Lively discussion has been stimulated by the question 
of intellectual maturity and decline. Popular indignation 
or alarm was aroused when, on the basis of the army 
testing data, the report was voiced about that the aver- 
age American male had the mentality of a 14-year-old 
child. This simply meant, of course, that the comparison 
of Stanford-Binet and Army Alpha scores of a representa- 
tive group of soldiers in the United States army indicated 
that the average individual does not improve beyond the 
age of 14 in performance on common intelligence tests. 
These findings have subsequently been questioned, how- 
ever^jiiore recent investigations ,,,.such.. as those of Tea- 
garden (13) and Thorndike (14) haying placed the "limit 
of intellectual growth" in the late teens or early twenties. 
In general, mental development seemed also to continue 

longer in subjects of 
higher educational 

A closely related 
question concerns the 
decline of mental ac- 
tivity. Jones and 
Conrad (8) gave the 
Army Alpha to 1191 
individuals between 
the ages of 10 and 
60, living in 19 vil- 
lages in rural sec- 







30 40 

Chronological Age 



NEW ENGLAND GROUPS. (After Jones and Con- 
rad, 8, p. 241.) 

tions of New England. In Table VII are shown frequency 
distributions as well as averages and standard deviations of 


successive age groups. The age changes in average score are 
shown graphically in Figure 30. It will be seen that the aver- 
age score rises from 44.4 at age 10 to 100.7 at 19-21. Be- 
yond this there appear irregular and small drops. Even for 
the oldest group tested, the drop is not very large. Selective 
factors may account in part for these findings. Among the 
older groups there were more individuals who pleaded ex- 
emption from the test because of failing eyesight, difficulty 
in reading, and similar reasons. The less intelligent and 
less energetic older subjects, furthermore, were less likely 
to come to the community centers where the tests were 
given, as was evidenced by the fact that subjects tested 
in their own homes showed a much sharper age decline 
than those tested in community centers. An analysis of 
age curves of the different tests in Army Alpha revealed 
fundamental differences from test to test, the curves for 
"naming opposites" and " general information," for ex- 
ample, showing no decline with age. 

In regard to variability, it should be noted that indi- 
vidual differences were large at all ages, as shown both 
by the distributions and by the size of the standard 
deviations. Overlapping of different age groups is very 
marked, the range of scores within any one age group 
being much greater than the largest average difference 
between groups. Finally, the standard deviation shows a 
fairly clear-cut tendency to rise with age, even though 
selective factors would tend to make the older groups 
tested more homogeneous than the younger. It is inter- 
esting to find that the standard deviations of the older 
groups are larger than those of the younger in spite of 
the fact that the averages decrease with age. For exam- 
ple, the 50-54 year group has an average of 81.3, slightly 
lower than that of the 15 year group which is 85.7. The 
standard deviation of the former, however, is 43.1 as 


compared to 32.3 for the younger group. Thus the changes 
in .standard, deviation with age seem to be something 
more than a , statistical artifact which might result from 
the. changes. In size of scores. As the individual has more 
experiences and is subjected to a wider variety of environ- 
mental stimulation with increasing age, more possible 
sources of variation are thereby introduced and individual 
differences will continue to increase indefinitely. 

Willoughby (19), in his investigation of family resem- 
blances in mental traits, also compared averages and 
standard deviations on each of II tests 1 for successive 
age groups from childhood to 60 years. The scores again 
rose until the late teens or early twenties. Beyond that 
age, however, the different tests presented somewhat vary- 
ing pictures. A marked decline in score was found in tests 
of series completion, analogies, opposites, substitution 
learning, history-literature information, and making com- 
parisons. In arithmetic reasoning, on the other hand, 
no decline was exhibited. The latter task is one which is 
more useful and more frequently met in everyday life. 
The decline of the older groups in most tests which do 
not enter into ordinary adult activities could be attrib- 
uted to the fact that the formal education of the older 
subjects is more remote and probably less in amount. The 
general level of education has increased phenomenally 
during the past 50 years, a fact which cannot be ignored 
in comparing older and younger groups. 

Miles and Miles (9) conducted a comprehensive survey 
of age changes in ' intelligence test scores. A total of 
823 persons ranging in age from 7 to 94 were given a 
special adaptation 2 of the Otis Self-Administering Intelli- 

1 See Ch. IV for fuller description. 

2 Consisting of the first 60 items of the test, given with a 1 5-minute time limit. 
The scores so obtained, however, were found to correlate highly with scores on 
the 30-minute test, on various groups. 


gence Test. The averages and standard deviations shown 
in Table VIII are based on 617 adults of both sexes tested 
in one city and are typical of the general findings. The 
averages show practically no change between 15 and 29; 
between 30 and 50 there are very small but consistent 
decreases; beyond 50 the decline is more rapid and con- 
tinues up to the highest age group tested. Variability 
indicates no consistent change with age unless it be a 
slight increase during the middle period between 40 ar^d 
50, as compared to the youngest and oldest groups. This 
is in general agreement with the findings of other studies 
reported above. Wide individual differences were ob- 
served within all age groups, with marked overlapping. 


(After Miles and Miles, 9, p. 53) 


of Cases 




of Cases 


















ii. 16 
















































The correlations between each individual's score and 
his age brought out the same trends suggested by the 
comparison of averages. The correlation throughout the 
entire adult age range, from 20 to 95, was approximately 
.50, showing a clear-cut tendency for the older persons 
to make lower scores. 1 When only individuals between 

1 Similar results have recently been obtained in a study on a small group of 
"mentally normal" hospital patients who were submitted to an intensive testing 
program (18). 






15 - 

15 and 55 are included, the correlation is .283; when 
Dnly the older subjects between 50 and 95 are employed, 
the correlation rises to .372. This suggests a more rapid 

rate of decline during the 
upper ages, thus corrobo- 
rating the findings on aver- 
ages. The fact that all the 
correlations are far from 
a perfect i.oo is attrib- 
utable to the wide individ- 
ual variation within age 
groups and the overlap- 
ping of different age 

As a further analysis 
of age changes, the sub- 
jects were classified into 
four groups in respect to 
the amount of formal 
education which they had 
received. In Figure 31 
will be found the four 
curves, A to D, showing 
the average score of each 

educational group at successive decades between 20 and 80. 
The groups were constituted as follows: 

Group A four years of college plus additional grad- 
uate or professional training 

Group B one year of college and higher (includes 
group A) 

Group C one to four years of high school or its equiv- 

Group D eight grades of elementary school or 


Beyond College 

College and Beyond (1-10 

years; includes the above) 
High School or Equivalent (1-4 years) '' 

-Grade School (0-8 years) 

i 1 i i 

20 30 40 50 60 70 80 
Chronological Age 



Although all groups show a decline from the lower to 
the^ggpTer "age levels, this decline is smaller for the higher 
educational Jgtcmjts* The curves do not cross, individuals 
in the higher educational groups obtaining higher average 
scores than those in the lower groups at all ages. It is 
also interesting to note that the lowest point on curve A, 
reached by the 70 year group is still higher than the 
highest points of curves C and D. TJIUSLJ* yo-year-old 
person .who had pursued at least one year of graduate 
work would be expected to score higher than a 2O-year- 
613 elementary ,or High school graduate. The significance 
of this finding will be elaborated below, in conjunction 
with other data. 


In a series of varied and extensive experiments on adult 
learning, Thorndike (16) found no appreciable, decline in 
this ability between the ages of 20 and 45. Several groups 
of adults were put through a long period of training in 
different tasks and their progress was observed. The 
groups varied from an intellectually and educationally 
superior group of graduate students, through more nearly 
average subjects attending evening high schools and secre- 
tarial schools, to a somewhat inferior group of Sing Sing 
prisoners. The major findings have been summarized in 
Table IX. In each task, the gain through practice made 
by an older group (35 or over) has been expressed as a 
percent of the gain made by a younger group (20-24) 
under the same conditions. Thus, if the percentage is 100 
it indicates that the two groups made equal gains; if it is 
less than 100, the younger group gained more; if over 100, 
the older gained more. 

1 For a comprehensive survey of studies on adult learning, the reader is re- 
ferred toRuch (n). 

i 7 6 


It is apparent from the data of Table IX that age 
differences in favor of the younger group are larger in the 
more meaningless rote learning tests and are absent or 
reversed" in the more practically useful and meaningful 
functions. In most tasks, the older person could compen- 
sate for any deficiency in learning capacity by greater 
interest and effort and by a larger fund of relevant past 


(After Thorndike, 16, p. 103) 



Gain of older group vy 

/-> ' r ^ *^ 

Gain ot younger group 


i. Drawing lines of given 
length, blindfolded 
2. Writing with wrong hand 
3. Transcribing words in code 
4. Memorizing code used in 3 
5. Learning Esperanto 
6. Memorizing paired num- 
bers and syllables 
7. University studies 



over I oo (estimated) 

Prisoners of 

I. Number-letter substitu- 
tion from key 
2. Elementary school studies 
3. Special addition practice 


High School 

I. High school studies: Eng- 
lish, algebra, civics, etc. 



I. Typewriting 
2. Stenography 

Approximately 95 * 


* Older group was 30 or over, rather than 35 or over. 


experience. Thorndike gives many examples of this fact, 
in addition to his main findings. Thus the group of uni- 
versity students progressed over twice as fast in learning 
Esperanto 1 as 9- to iS-year-old pupils in a good private 
school, although the former had spent less than half as 
much time as the latter in studying the language. Sim- 
ilarly, the adult prisoners learned elementary school sub- 
jects faster than average schoolchildren. 

the attempt further to interpret his results, Thorn- 
tlliat two of the tasks employed with the 
g r ?up?, ^-? ..drawing lines blindfolded and inqi- 
.pf a code, measured "sheer mo.difiabiUty, 

or learning ability, more directly than the other t&sks, 
since-thfi^jK^S .relatively independent of past experience. 
Drawing chiefly from the findings on these two tests, 
he ventured the estimate 
that there is a decline in 
" sheer modifiability" of w 
approximately 15% be- p 
tween the ages of 22 and 

42, a negligible loss of less w 20 so 40 so 

, tS TT i Chronological Age 

than i% a year. He also p ^ ^ A 


presents, on this basis, an CHANGES IN LEARNING ABILITY. (After 

estimated curve of age Thorndike > l6 < P- ^ 

changes in "sheer modifiability" from childhood to mid- 

dle maturity. This curve is reproduced in Figure 32. 

The study of adult learning was extended into the 
higher age levels by Ruch (12). Three groups of subjects 
were employed, 40 in each of the age groups 12 to 17, 
34 to 59, and 60 to 82. The tasks to be learned included 
two motor and three verbal. Of the motor tests, one 
involved a simple visuo-motor coordination in direct vi- 

1 One of the proposed "universal languages," characterized by a very system- 
atic and logical structure in contrast to current languages. 



sion; 1 the other consisted of the same task performed in 
mirror vision, thus involving the establishment of re- 
actions which were opposed to the subject's past experi- 
ence. All of the verbal tasks involved the learning of 
paired associates. The first consisted of word pairs having 
some meaningful connection, such as nest-owl, soft-chair. 
The second was made up of "nonsense" material, such 
as A X M = 5, N X M = C, and was thus relatively- 
neutral in regard to past association. The third necessi- 
tated the breaking down of old associations, the material 
consisting of false multiplications, such as 5 X 4 = 2 > 

3 X i i. 

In Table X will be found the averages and standard 
deviations of the three groups on each test. Without a 
single exception, the averages show a progressive decline 
from the young to the middle and from the middle to 
the old group. The age differences are largest, however, 
nTthose tests whicli are hindered, by ordinary past experi- 
ence and smallest in those which are aided by such 


(After Ruch, 12, p. 277) 



Standard Deviations 







Motor learning: 

I. Direct 







2. Mirror 







Paired associates: 

i. Meaningful 







2. Nonsense 







3. False multipli- 


1 06. 1 






*A modified form of the Koerth pursuit rotor, in which the subject must 
follow a rapidly and irregularly moving object with a stylus. 


Ruch demonstrates this by comparing the critical ratios 1 
of the differences for each test. These are shown below 
for the differences between young and old groups, middle 
and old, and young and middle, respectively. 

Y-0 M-O Y-M 

Motor: Direct vision 6.1 5.4 0.9 

Motor: Mirror vision 8,5 6.4 0.6 

Meaningful associates 5.4 2.3 3.9 

Nonsense associates 7.2 4.0 2.9 

False multiplications n.6 4.7 5.9 

In both the Y-O and M-O comparisons, the results appear 
to be very consistent. Mirror vision learning shows greater 
age decline than direct vision learning; within the paired 
associates, there is a progressive rise in difference as we 
go from the meaningful associations, through the neu- 
tral nonsense material, to the interference material of 
the third test. The comparison of young and middle 
groups yields somewhat less consistent results, probably 
because these differences are all small and not very 

An examination, qf, the standard deviations in Table X 
reveals" a rather consistent rise in variability with age, in 

XMJ- ^ BJ ^ , papam*"'" **'*'*' "- **' .t.u,.,w.),, ,, , , ,,i,,, ,, , , , , , ' * 

spite" of the equally consistent , .drop ia averages. The 
standard deviations of the oldest group are all larger 
than those of the youngest with only one exception, viz., 
the mirror vision test. In the case of the middle group, 
all standard deviations are higher than those of the 
youngest, with no exceptions. These findings are in 
agreement with the analysis of age and variability given 

1 Critical ratio = > a common statistical device for estimating the 


"reliability" of a difference. When the critical ratio is equal to 3 or more, it 
indicates that the obtained difference could not have resulted from chance errors 
of sampling, and such a difference is therefore regarded as reliable. 



^jnay jaow attempt to synthesize the findings of 
..these various investigations and to evaluate them in the 
light of the studies on training discussed in the preceding 
.chapter* If we think of all mental development in terms 
of learning, the diverse findings both on the upper limit 
of mental growth and on the decline of ability can be 
fitted into an intelligible pattern. It might be objected 
that the learning curve shows no decline, whereas age 
curves do. This apparent inconsistency results, however, 
from an incomplete statement of the situation. The 
problem will be considerably clarified if we speak of age 
changes in specific tasks, as we do in the case of learning, 
rather than discussing mental development in general. 
It is quite true that the cumulative effects of learning in 
everyday life will increase proficiency indefinitely in 
certain tasks, but such learning will just as surely inter- 
fere with the performance of other tasks. If the general 
effect of any specific act of learning upon all of the indi- 
vidual's behavior is considered, it becomes apparent that 
learning may cause a decline as well as a rise in achieve- 

Thjo.dediiie^^^ psychological tests 

with age is no longer-surprising when .;we,xealize the re- 
semblance of all such .tests. to. school work. We should 
therefore expect that the longer the individual has been 
out of school, the more chance he has had to forget what 
he learned as a child, through interference from other 

Although in his everyday life the adult may be employ- 
ing much that he learned in school, he is at the same time 
losing many school habits, such as working with a specific 
time limit, following directions literally although he may 


see little sense in them, and especially working with mate- 
rials which may be meaningless and of no apparent use 
to him. When a schoolchild is confronted with a psycho- 
logical test, the novelty, strangeness, and apparent pur- 
poselessness of many of the things he is asked to do will 
not disturb him unduly, since at that age he is still doing 
many things for which he can see no immediate value. 
Such tasks are accepted by the child as part of his every- 
day work. Not so with the adult. The older he grows, 
the more he concentrates only on those activities which are 
either of practical significance or directly pleasurable to 
him. The reaction of many adults to intelligence tests, 
as contrasted to that of schoolchildren, illustrates this 
difference. To most adults, such a test is either foolish or 
entertaining. The adult is far more sensitive to the appar- 
ent impracticality of the situation than the child who is 
used to taking tests which to him are almost equally 

That adult ability does not decline in all tasks is demon- 
strated By the obvious Improvement in functions related 
to the individual's daily work. The achievements of 
many people progress along a continuously rising line 
throughout life. 

I^or can a distinction be legitimately made between the 
extent of a person's abilities, which increases con^ai^tly 
wij:h age, and the level or difficulty oi-ta^^w]^K,J^J>s 
capable of mastering. 1 The latter is definitely dependent 
upon the former. As was brought out in the discussion 
of practice and variability, thejcnore^^ 
Uar^dfcj&a^ A problem which 

is commonly regarded as difficult and which can be solved 
by only a few individuals is one which involves the synthe- 
sis of more numerous and varied types of learned behavior, 

1 Such a distinction has been suggested by Thoradike (15), 


We should say, for example, that the derivation of a 
formula which requires a knowledge of arithmetic, alge- 
bra, trigonometry, and calculus is more difficult than one 
which can be derived simply by the application of princi- 
ples of arithmetic and algebra. If we define the difficulty 
of a task objectively in terms of the number of people who 
can perform it correctly, it will unquestionably prove to 
be a function of the number of different specific abilities 
involved. Even if a more subjective, popular definition 
of difficulty were suggested, it would doubtlessly be found 
to hinge upon the same principle. 

Many of the previously reported findings are clarified 
by such a view of mental development. ,,,Xhu3,,the slower 
decline in intelligence test performance of adults who 
have had a longer period of schooling is to be expected 
when we recall that such education is, relevant to the 
tasks on the tests themselves. The formal education 
which is characteristic of our culture is of a verbal and 
abstract sort and it is from these fields that intelligence 
tests draw predominantly for their material. All groups 
have been constantly subjected to training, but of a dif- 
ferent sort. In a test of manual operations, for example, 
we should expect a more rapid decline with age among 
the " better educated" professional classes than among 
certain groups of factory workers. 

JForj:he ;jsame reason, the limit of intellectual improve- 
ment, as measured by conyjioa . .iirt,dUigCTP.e..test3, . .will be 
reached later by those groujgsj^hich continue their formal 
schooling to a later age. This has been repeatedly demon- 
strated in studies on the "point of cessation" of mental 
growth. Corroboration of the proposed interpretation of 
age changes in mental traits can also be found in the 
experiments on adult learning. Thusjfjv^^ 
that Thorndike found a difference in rate of decline be- 


tween the .more, "meaningless" and thejDooze,, " 

ful" and useful tasks j and Ruch found a, similar difference 

between those tasks which were aided and those which 

were hindered by the common training furnished in ur 


Finally, mention should be made of a possible physio- 
logically determined decline in mental activity with age, 
apjLCLJrom.cliajiges correlated .with beaming. The effect 
of the deterioration of necessary structures doubtlessly 
plays a part in the marked and sharp decline in all psycho- 
logical functions which frequently characterizes very late 
old age or senescence. 1 Such obvious handicaps as fall- 
ing vision and hearing, and muscular and neural deteriora- 
tion can hardly fail to affect all the individual's activities. 
These changes, however, do not set in to an appreciable*ex- 
tent until very late in life and consequently, cannot very 
plausibly, be.-ofoed as -an explanation ^ofthe-deeMfie in 
mental test performance during earlier -matority. There 
are cases, furthermore 3 in which serious structural handi- 
caps during old age have been compensated to a remark- 
able degree by interest, effort, and the advantages of past 
experience. The wide individual differences found at differ- 
ent ages also bespeak the potency of specific environmental 
circumstances rather than physiological conditions charac- 
teristic of a given life period. 

It would seem that the physical handicaps of senescence 
are of the same nature as the physical inadequacies of 
the immature child; they set the upper limits of behavioral 
development at a given chronological period, but they 
do not determine the degree to which such limits will be 
approximated. It seems, also, that these physically set 

1 For a discussion of the physiology of old age, and for descriptive accounts 
of behavior in senescence, the reader is referred to Child (2), Hall (6), and 
Hollingworth (7). 


limits are always much higher than is commonly sus- 
pected, since training and stimulating conditions can at 
all ages accomplish surprising results. 


1. Baldwin, B. T., and Steelier, L. I. "Mental Growth Curves 
of Normal and Superior Children/' Iowa Univ. Stud. Child 
Welfare, 1922, 2, No. I. Pp. 61. 

2. Child, C. M. Senescence and Rejuvenescence. Chicago : Univ. 
Chicago Press, 1915. Pp. 481. 

3. Courtis, S. A. "Maturation Units for the Measurement of 
Growth," Sch. and Soc,, 1929, 30, 683-690. 

4. . Growth and Development in Children (repr. from 

Advances in Health Educ,}. N. Y.: Amer. Child Health 
Assoc., 1934. Pp. 180-204. 

5. Freeman, F. N. Mental Tests. N. Y.: Houghton Mifflin, 
1926. Pp. 503. 

6. Hall, G. S. Senescence. N. Y.: Appleton, 1923. Pp. 517. 

7. Hollingworth, H. L. Mental Growth and Decline. N. Y.: 
Appleton, 1927. Pp. 396. 

8. Jones, H. E., and Conrad, H. S. "The Growth and Decline 
of Intelligence," Genet. PsychoL Mon., 1933, 13, 223-298. 

9. Miles, C. C., and Miles, W. R. "The Correlation of In- 
telligence Scores and Chronological Age from Early to Late 
Maturity," Amer. J. PsychoL, 1932, 44, 44-78. 

10. Miles, W. R. "Age and Human Ability," PsychoL Rev., 
I933> 4Q> 99-123. 

11. Ruch, F. M. "Adult Learning," PsychoL Bull., 1933, 30, 

12. . "The Differentiative Effects of Age upon Human 

Learning," /. Gen. Psychol., 1934, n, 261-286. 

13. Teagarden, F. M. A Study of the Upper Limits of the De- 
velopment of Intelligence. N. Y.: Teachers College, Colum- 
bia Univ., Bur. Pub., 1924. Pp. 112. 

14. Thorndike, E. L. "On the Improvement in Intelligence 
Scores from Thirteen to Nineteen," /. Educ. PsychoL, 1926, 
*7, 73-76. 


15. Thorndike, E. L., and staff. The Measurement of Intelligence. 
N. Y.: Teachers College, Columbia Univ., Bur. Pub., 1926. 
Pp. 616. 

1 6. Thorndike, E. L., et aL Adult Learning. N. Y. : Macmillan, 
1928. Pp. 335. 

17. Thurstone, L. L., and Ackerson, L. "The Mental Growth 
Curve for the Binet Tests," /. Educ. Psychol., 1929, 20, 

1 8. Weisenberg, T., Roe, A., and McBride, K. E. Adult In- 
telligence. N. Y.: Commonwealth Fund, 1936. Pp. 155. 

19. Willoughby, R. R. "Family Similarities in Mental Test 
Abilities," Genet. Psychol. Mon., 1927, 2, 235-277. 



In the discussion of age changes in mental traits during 
childhood as well as senescence, mention has been made 
of certain upper limits of development set by physical 
condition. As was repeatedly pointed out, such struc- 
turally imposed limitations are less important than is 
commonly supposed, since the individual rarely attains 
the degree of development set by his physical capacity at 
any age. We majr still inquire, however,, whether physical 
differences "among individuals exert an , appreciable influ- 
ence upon their mental differences. It is apparent that 
extreme sensory defects, for example, can so profoundly 
handicap the individual that even special training will 
not bring him up to a normal level of performance. Simi- 
larly, other parts of the reacting organism may, by their 
deficiency or superior condition, play a part in the de- 
velopment of mental traits. It should be kept clearly in 
mind, however, that structural characteristics, insofar as 
they are shown to influence mental development, can be 
regarded only as necessary conditions; thepresence^pf a 
rqguired physical f actor Jdoes_ not jinj^ 
havioral development, ^ut^ ^mply ,. m^kea J&e M^I JE2 8 "" 

The question of the relationship between mental and 
physical characteristics has long proved a fascinating 
one to man. The field has abounded with fanciful specula- 
tions and vain hopes that a person's character or intelli- 
gence could be "read" from physical signs. Recently, 



the problem has been approached more empirically and 
objectively and a sizable body of data has been accumu- 
lated on the relationship between various structural, 
physiological, or sensory conditions and psychological 
traits. There are a number of well-known types of mental 
and emotional disorders which are directly traceable to 
the effects of drugs or infection on the nervous system, 
the deterioration of tissues, and the like. ^ Thus general 
paresis results from syphilitic infection, delirium tremens 
from excessive habitual use of alcohol, cretinism from a 
deficiency of the thyroid gland, encephalitis lethargica l 
from a bacterium which is believed to enter through the 
nasal passages. Many other similar conditions could be 

In the present discussion, however, we shall deal only 
w jQp^5g-^j5jjgg^"g;' e g rees o f variation commonly found 
^^j^.^^.^1 ran g e Q individuals. We are not con- 
ceffiet^witK'"'in6re extreme and pathological conditions, 
since they are relatively rare and their effects upon be- 
havior are more obvious. Tli^j^^r^^^uig^^ the 
relationship of behavior. traits, to craju&i, and facial, Char- 
acteristics, , tady build, ptiysiolpgical qonditio3a% a&d sen- 
sory defects will be surveyed briefly and illustrative 
investigations reported. Some further data on anatomical 
characteristics with special reference to theories of con- 
stitutional type will be presented in the following chapter. 


Popular interest in the size and shape of the skull was 
considerably stimulated by the pseudo-science of phre- 
nology, 2 initiated by Gall in the eighteenth century. 

1 Often popularly called "sleeping sickness," although not identical with 
African sleeping sickness. 

2 For a discussion from the viewpoint of a practicing phrenologist, see 
Fowler (4). 


Phrenology was based on a false notion of the functions 
of the various parts of the cerebral cortex. Thus the 
phrenologists claimed that each part of the brain con- 
trolled a particular intellectual or moral function such 
as mechanical ingenuity, veneration, domestic impulses, 
and other equally complex and vaguely defined activities. 
They asserted further that the over- or underdevelopment 
of such characteristics could be detected by examining 
the protrusions on the skull. The location of a particu- 
lar "bump" was taken to mean that the function whose 
cortical area was supposed to be beneath it was over- 
developed in the given individual. 

It would seem unnecessary to refute such an obviously 
untenable doctrine were it not for its still widespread 
popularity among the general public and its lucrative 
current practice by quack "vocational counsellors" and 
similar soothsayers of modern times. In the first place, 
phrenology is founded on the erroneous assumption that 
there is a perfect correspondence between the shape of 
the skull and that of the brain; this is hardly to be ex- 
pected in view of the several layers of membrane and 
the cerebro-spinal fluid which intervenes between the two. 
Size, furthermore, cannot be regarded as a sufficient index 
of degree of development in the nervous system; the 
latter seems to depend more closely upon the complexity 
of interrelation of the microscopical nerve cells. Experi- 
ments on cortical localization have demonstrated a con- 
nection between certain muscle groups or sense organs 
and certain brain areas; but this is quite unlike the phre- 
nologist's attempt to map out complex personality traits. 

Phrenologists have also tried to show that cranial 
capacity as a whole, or total brain size, is related to intelli- 
gence. As in all their data, however, they draw their evi- 
dence from selected examples. It is true that a certain 


type of idiot, the microcephalic, has a very small skull, 
but there are also idiots with normal or very large skulls. 
A few men of genius may be found with very large brains, 1 
but some are likewise found with small brains. The 
question can only be settled by accurate measurement of 
large numbers of unselected cases. 

Investigations on the relationship between cranial ca- 
^acity^nr^ Intellectual achievement, have generally 
yielded negative results. In a number of studies in which 
average cranial dimensions of bright and dull groups were 
compared, the data are ambiguous and difficult to inter- 
pret. 2 The differences between the averages are always ex- 
tremely small and occasionally inconsistent from one com- 
parison to another. In many cases the measures taken on the 
living skull were not good indices of brain capacity. The 
groups employed varied widely in age and, especially when 
children are included, this may produce a spurious relation- 
ship between size of head and intelligence since the older 
subjects will have larger heads and at the same time will ob- 
tain higher scores on intelligence tests. Finally, the esti- 
mates of intelligence were frequently crude and unreliable. 

The first well controlled study on cranial measurement 
in which adequate correlational analysis was employed is 
that of Pearson (17). Measures of head length, head 
breadth, and cephalic index 3 were obtained on three 

1 A frequently quoted example is Daniel Webster, whose head circumference 
measured 24! inches. 

2 For a survey of these data, see Paterson (16). 

,, , ,. T i 100 X head width , . - , , , f , 

3 Cephalic Index = * Length of head is measured from, the 

head length 

space between the eyebrows to the farthest projection at the back of the head; 

head width, or breadth, is the distance from left to right sides, measured from 

the points of maximal protrusion above each ear. The following is a common. 

classification of cephalic index: 

Dolichocephalic, or long-headed C.I. below 75 
Mesocephalic, or medium-headed C.I. between 75 and 80 
Brachycephalic, or broad-headed C-I- above 80 


groups, including 1010 Cambridge University students, 
over 2200 12-year-old schoolboys, and over 2100 12-year- 
old schoolgirls. 1 It will be noted that age was held con- 
stant among the children by selecting only 12-year-olds. 
The subjects were classified into intellectual levels on the 
basis of teachers' ratings and scholastic records. The 
correlations between intellectual level and cephalic index 
were .06, .04, and .07 among the university students, 
schoolboys, and schoolgirls, respectively. For length of 
head, the correlations in these three groups were .11, .14, 
and .08, and for breadth of head .10, .11, and .11. These 
correlations speak for themselves, being too low in every 
case to indicate any appreciable trend. The very low and 
inconsistent correlations with cephalic index lend no 
support to a frequently proposed theory that the "long- 
headed" individuals, with a low cephalic index, are the 
more intelligent, nor to the opposite view, also occasionally 
voiced, that the "broad-headed," with high cephalic 
index, are the more intelligent. 

More recent investigations by the correlation method 
have in general substantiated Pearson's findings. Mur- 
dock and Sullivan (14) report a correlation of .22 between 
head diameter, obtained by averaging maximum head 
width and maximum head length, and I.Q. 2 on about 596 
elementary and high school pupils. By the use of I.Q.'s 
and by the conversion of physical measurements into 
deviations from the average of each age-sex group, the 
influence of age was held constant. Sommerville (27) 
found correlations of .10, .03, and .09 between head 
length, head width, and head height, respectively, of 
100 male college students and their scores on the Thorn- 
dike Intelligence Examination for High School Gradu- 

1 The number of cases differed slightly for each measure. 

2 Found from a number of group intelligence tests. 


ates. The correlations were no higher between intelligence 
test scores and cranial capacity as estimated from the 
three given head dimensions. Employing one standard 
formula for the computation of cranial capacity, Sommer- 
, ville obtained a correlation of .11 with intelligence test 
score; with another formula, the correlation was .10. 
Reid and Mulligan (23) found a correlation of .08 be- 
tween cranial capacity and scholastic achievement on 
449 male medical students in Scotland. Cranial capacity 
was calculated by taking the product of head length, 
breadth, and height, with allowance for thickness of dif- 
ferent parts of the cranium. Scholastic achievement was 
determined by performance on standardized examinations 
in three courses which were taken by all the students. 

It seems quite definitely established, then, that no 
appreciable relationship exists between intellectual per- 
fofmance and either absolute, head , size, or,, head, shape;, as 
determined by the ceghalic index. Some dissenting voices 
are still heard, advocating the use of cranial measurement 
in the diagnosis of intellectual defect, 1 but their evidence 
is very ambiguous and their arguments are untenable 
and inconsistent. Further data on more detailed cranial 
conformation will be presented in the following section 
in conjunction with facial measurements. 


There are at present many firmly entrenched beliefs 
regarding the "meaning" of various facial and other bod- 
ily characteristics. The high forehead as an index of in- 
tellectual talent, the shifty gaze to denote deceitfulness, 
the firm chin and square jaw of determination, the taper- 
ing fingers of the artist, and a host of other traditional 

1 Cf., e.g., Porteus (21). 


associations which the reader can easily name have found 
their way not only into poetry and fiction but into the 
snap judgments and " hunches" of everyday life. We also 
frequently hear of alleged personality differences between 
blondes and brunettes, between blue-eyed and brown-eyed 
persons, or between those with a "convex" and those 
with a "concave" profile. Most of these beliefs are joined 
loosely under the general term "physiognomy." The latter 
is still being practiced as a financially profitable "system" 
of character analysis. 

A series of very accurate investigations to check many 
of the assertions of physiognomy were conducted under 
the general direction of Hull (12). The relationship be- 
tween convexity of profile and several personality traits, 
which is stressed by many commercial physiognomists, 1 
was studied by Evans (3). The subjects were 25 college 
women, all of whom were members of the same sorority. 
Such a group was chosen because of their close acquaint- 
ance with each other and their resulting ability to rate 
each other with a fair degree of accuracy. For the same 
reason, all individuals who had not been members long 
enough to be well-known were excluded from the study. 
Each girl ranked the remaining 24 in six personality traits, 
including optimism, activity, ambition, will power, domi- 
nation, and popularity. The average or consensus rank 
of all 24 judges on each girl was computed as a final es- 
timate for each trait. The subjects were also rated in a 
similar way for degree of blondness. A specially devised 
mechanical instrument was employed to read off directly 
the "angle of convexity" of the profile. In order not to 
omit any possibilities, convexity was measured in five 
different ways, such as whole face, upper face only, con- 

1 Cf., e.g., Blackford, K., and Newcombe, A. The Job, the Man, the Boss. 
N, Y.: Doubleday, Page, 1919 (p. 154). 


vexity without including the nose, and so on; height of 
forehead was also measured. 

The correlations between each of the measures of con- 
vexity or height of forehead and each of the six personality 
traits were low and often inconsistent with expectation; 
thaTTs, a correlation which would have been expected to 
be negative on the basis of the physiognomists' claims was 
positive, and vice versa. The highest correlations were a 
+.39 between convexity of whole face with nose omitted 
and " activity" rank, and a .39 between height of fore- 
head and "will power" rank. Even these correlations, 
however, are not significant in view of the small number 
of subjects, and they could have resulted from chance 
errors of sampling. The correlations for blondness range 
from +.28 with will power to .26 with optimism. These 
are also too low to be significant. 

A further point to bear in mind in evaluating these cor- 
relations is that the existence of a widespread bias among 
the judges regarding the association of facial and person- 
ality characteristics might in itself produce a correlation. 
Since tests were not available for the traits under con- 
sideration, it was necessary to resort to associates' judg- 
ments; but this procedure is inconclusive when prevalent 
popular beliefs are present. 

Facial and cranial measurements were combined in a 
study by Sherman (25). A group of 78 freshmen in an 
engineering college were measured by means of a specially 
designed "radiometer." A total of 15 distances and 4 an- 
gles were obtained on each subject, and each of these 
measures was then correlated with academic grades as an 
index of scholastic achievement. The correlations with 
the combined grades on all courses ranged from .26 to 
+ .34. It is interesting to note that height of forehead 
correlated .15 with academic grades. This corroborates 


the low negative correlations found by Evans between 
height of forehead and several personality traits which 
might be expected to manifest themselves in school work. 
If such a tendency were established, it would indicate a 
reversal of the popular notion of a "high-brow" ! 

Various similar studies have been conducted by many 
investigators. In Hull's laboratory, an investigation was 
carried out to determine whether there is any relationship 
between the shape of the hand and a number of traits 
suggested by "chirognomists." The results were definitely 
negative. Numerous experiments have been conducted to 
discover whether it is possible to judge intellectual or 
emotional traits from photographs, as ,we should expect 
if these traits were manifested in facial characteristics. 
All of these investigations, although revealing many in- 
teresting cases of agreement among judges which suggest 
widespread popular beliefs or a conventionalized facial 
symbolism, showed no agreement with independent crite- 
ria of the traits, such as intelligence test scores or observa- 
tions of behavior. 

It should be pointed out in conclusion that even when 
significant correlations are found between certain facial 
or cranial characteristics and psychological traits, as in 
the case of a few of Sherman's measures, the correlations 
are still too low to give any information about individuals. 
They simply indicate a general trend in the group which 
may result from a few extreme cases,, Insofar as the cor- 
relation is far below i.oo, it shows that there are many 
individual exceptions to the general trend. The presence 
of such exceptions or reversals of relationship proves that 
whatever influence any physical factor may exert upon 
behavioral development is very minor and can easily be 
obscured by other more potent factors. 

A further fact to note is r thj^as^lon^as a certain notion 


]sjvidejy, .prevalent, reg&cdJBg the, association of, a giypn 
physical characteristic with a mental or emotional trait, 
thiTTnay in itself influence the individual's develppmeut. 
If a person is commonly mistrusted by his associates and 
is not given any responsibility, it is difficult for him to be 
open and sincere; if a child is regarded as dull and stupid, 
he may easily come to believe it himself and act accord- 
ingly. The social and motivational influence of a wide- 
spread prejudice cannot be ignored. A vicious circle 
is initiated by such a situation; the more widespread 
the prejudice, the more effective it will be and the more 
evidence can therefore be found which seems to sup- 
port it. 

From these considerations it is, apparent that any rela- 
tionship which may exist between facial characteristics 
and psychological traits cannot be large. Even the very 
low degree of correlation occasionally found is far from 
being conclusively established because of many uncon- 
trolled factors. Should a slight correspondence be proved 
between certain facial or cranial conformations and behav- 
ior, it has beeiijsuggested that such association may result 
from a common dependence of both types of characteris- 
ticTujpbn some underlying condition. T^e,, activity f of the 
en4ocrine glands offers possibilities for such a Connection. 
In certain extreme pathological cases as, for example, 
thyroid deficiency, the resulting condition includes char- 
acteristic physical as well as mental symptoms. It is 
barely possible that certain facial characteristics, as well 
as emotional or intellectual traits, are influenced within 
their normal range of variation by over- or underac- 
tivity of some endocrine gland. This, of course, is only 
speculation. The field of endocrinology is far too com- 
plex and too young. to offer any clear-cut answers to such 
a query. 



Gross bodily dimensions, proportion of trunk and limbs, 
height in relation to weight, and similar structural char- 
acteristics have also been suggested as possible indices of 
intellectual or emotional status. Since much of the mate- 
rial in this field has been collected to test out the various 
"type theories" proposed from time to time, the discus- 
sion in this section will be supplemented in the following 
chapter. Only the data on gross size and absolute measures 
will be treated here, the material on relative proportions 
and body type being reserved for Chapter IX. 

Similarly, we are not concerned with gross malforma- 
tions and pathological conditions. Many of these condi- 
tions, with which anyone who has seen circus "freaks" 
is familiar, have been definitely attributed to glandular 
disorders. Thus gigantism, a condition in which the in- 
dividual may attain a height of seven or eight feet, 1 results 
from oversecretion of a pituitary hormone; dwarfism, or 
stunted growth in which the bodily proportions are nor- 
mal, is produced by insufficient pituitary secretion. No 
definite intellectual defect has been demonstrated in these 
cases. Cretinism, associated with an underactive thy- 
roid, is characterized by abnormal bodily development 
and proportions as well as by intellectual defect, sluggish- 
ness, and other behavioral disturbances. If we exclude 
cases which manifest obvious glandular dysfunctions or 
other pathological conditions, we still find a wide range in 
height and weight within the general population. It is 
into the relationships of these variations with behavioral 
characteristics that we now wish to inquire. 

As in the case of cranial measurements, interest in body 
build has long been manifested. The search for a possible 

1 The "giant" with the Ringling Bros.-Banrum & Bailey circus is reported 
to be 8 feet, 6 J inches tall 


relation between body dimensions ^nd intellect probably 
received a strong impetus from the popular view that the 
intellectually gifted were deficient in other respects, and 
in particular that such individuals were weak, puny, and 
physically inferior. This notion of compensation was 
cherished widely because of its consoling character it 
was no doubt accepted as the device of a benevolent na- 
ture to "even things up." In the effort to overthrow theae 
unfounded beliefs, early research workers swung to the 
opposite extreme and asserted that the intellectually 
ablest were also the physically ablest, and that a close cor- 
respondence exists between physique and meatal ability. 

Galton (5), for example, suggested that the number,. of 
physically superior individuals among his groups of emi- 
nent" men (cf. Ch. IV) was greater than in the general 
population. Many studies on large groups of children 
have"" subsequently appeared which relied upon the com- 
parison of averages for their conclusions. 1 Such investiga- 
tions agree in finding a slightly higher average height and 
weight among the intellectually superior groups than 
among the normal, and slightly higher for the normal than 
for the dull. Intelligence was usually estimated quite 
crudely from school status or teachers' ratings. The 
differences in averages were invariably so slight and the 
overlapping of groups so large that the degree of correla- 
tion between height or weight and intelligence would 
necessarily be negligible. 

Investigations on the physical status of the feebleminded 
or the intellectually gifted child have yielded results which 
are equally difficult to interpret. When averages are 
compared, the feebleminded appear to be definitely below 
the norms in height and weight, and the bright children 
above the norms. In Terman's extensive investigation (29) 

1 For a summary of this literature, see Paterson (16). 



on gifted children, 1 a slight tendency was noted for the 
subjects to be above the age norms for American-born 
children In height and weight. L. S. Hollingworth (n) 
compared the heights of three groups, each composed of 
45 children between the ages of 9 and 1 1 . In the " superior" 
group were only children whose I.Q.'s were above 135 
(median LQ. = 151), in the "normal/' those with LQ.'s 
between 90 and no (median LQ. = 100), and in the "in- 
ferior/' those with I.Q.'s below 65 (median LQ. =43). 
The subjects in the three groups were carefully equated, 
each child in the one group being "matched" with a child 
in the other two groups in respect to age, sex, and racial 
background,, so that the influence of these factors was 
ruled out. In Table XI will be found a frequency dis- 
tribution showing the number of children in each group 
who fell within successive class-intervals in height, as 
well as the average height of each group. 




(After L. S. Hollingworth, n, p. 80) 

in Inches 


Group A 
(Median I. Q. = 151) 

Group B 
(Median LQ. = 100) 

Group C 
(Median LQ. = 
















(15), in her comprehensive survey of the 
characteristics of the feebleminded, obtained measures of 

1 Cf. Ch. XIII for fuller report. 


height and weight on 157 mental defectives in special 
classes and in various institutions. She^ found the same 

marked overlapping, 
the mentally defective children exceeding the 

median of normal children in weight and 45% in height. 1 
Goddard (7) collected extensive data on the height and 
welgHt of about n ? ooo mentally defective individuals, 
ranging in age from early infancy to 60 years, in 19 Amer- 
ican institutions for the feebleminded. In Figures 33 and 
34 are reproduced curves showing the average height and 
weight of successive age groups within four intellectual 
levels; the data on boys are given in Figure 33, those on 
girls in Figure 34. IJijmlLJ^ the curves of the 

four intellectual groups are practically identical at the 
lo^,, levels; the lower average iieight and weight of 
the mentally deficient groups becomes apparent oalyas 
adolescence and maturity are approadtied. 

Several factors may enter in to complicate the analysis 
of institutional data on the feebleminded. In the first 
place, those individuals with physical as well as intellectual 
defects are more likely to be committed to an institution. 
The feebleminded person who is physically fit or superior 
is less likely to be sent to an institution at all and more 
likely to leave the institution after he has received several 
years of training. Such individuals will have a greater 
chance to succeed in a routine occupation requiring 
strength and a good physique, with a minimum of thought 
and planning. The operation of such a selective factor 

r "**^*^^*.wi*4*<^ M *p-^'^ . y ' 'V^v^^'^'%''V7'-,^nr^wvrt 

might explain the divergence of Goddard s height and 
we^KiTcurves with age. Since only ^ ns ^^^^^^^ Qre 
tested, tKe inferiority at the upper ages could have resulted 
from the fact that the physically strongest and ablest had 

1 Complete overlapping would have been indicated if 50% of the feeble** 
minded group had exceeded the normal median. 






* 54 


| 50 


X 48 




I I ! I i I 8 i 









20 22 24 


12 14 16 18 

Age in Years 

BOYS AT SUCCESSIVE AGES. (After Goddard, 7, p. 228.) 




-i 130 

8 10 

22 24 


12 14 16 18 

Age in Years 

GIRLS AT SUCCESSIVE AGES. (After Goddard, 7, p. 229.) 


left the institution. In addition, the norms in terms of 
which these groups are evaluated may not be comparable 
at successive ages. As such norms are usually established 
on schoolchildren because of their greater accessibility for 
measurement, the norms at higher ages are frequently 
derived from high school students, a distinctly select 
group in respect to the general population. Finally, when 
fairly low grade feebleminded subjects are employed, it is 
very likely that several cases presenting special conditions 
such as cretinism are included and this would serve further 
to complicate the issue. 

results obtained more recently 

by the use of the correlation technique within "'normal" 
" groups, wilLbe, reported as more conclusive. Murdock and 
Sullivan (14), in the investigation cited above x found a 
correlation of .16 between I.Q. and weight (N = 595) and 
one of .14 between I.Q. and height (N= 597). In an 
investigation on 58 children in the kindergarten and 57 in 
the fourth grade, Gates (6) reports a correlation of .06 
between Stanford-Binet mental age and height, and .10 
between Stanford-Binet mental age and weight. 2 Pearson 
and Moull (18) correlated height and weight with esti- 
mates of intelligence in groups of 616 Jewish boys and 
580 Jewish girls living in London; the correlations between 
intelligence and height were .12 for boys and .11 for girls, 
and between intelligence and weight, .15 for boys and .07 
for girls. None of these values indicates a significant 
degree of relationship^ 

Data on older subjects have yielded, the same, general 
results, the correlations often being ,evJX lower, .since tjie 
groups were mpre select and covered a narrower rangy. 

1 In the section on cranial measurements. 

2 These correlations are the averages of four separate correlations for kinder- 
garten boys and girls, and fourth grade boys and girls. 


Brooks (2), employing 1118 subjects between the ages of 
13 and 20, in the third year of junior high school, the 
normal school, or the freshman year of college, correlated 
measures of height and weight with performance on sev- 
eral standardized group intelligence tests. Since correla- 
tions were computed separately for the two sexes and for 
several age groups, the subjects were classified into 17 
groups ranging in number of cases from 16 to 139. The 
height correlations ranged from .09 to +.26; those of 
weight ranged from .31 to +.26. Finally, in the study 
by Somrnerville (27) on college freshmen described above, 1 
a correlation of .16 was found between intelligence and 
standing height, .13 between intelligence and sitting 
height, and .10 between intelligence and weight. The 
majority of these correlations are positive but so low as to 
indicate little or no appreciable relationship between gen- 
eral bodily size and intellectual level when selective fac- 
tors and other irrelevant conditions are ruled out. 


Attempts have also been made to investigate the effects 
upon mental efficiency of various physiological conditions, 
such as general health, malnutrition, defective breathing, 
and focal infection from diseased tonsils, dental caries, 
and other sources. QuaM.lte, first comprehensive surveys 

Sta -* "'' M >t*i>.* u,* . < fr^ <M,m ?***" * "", i'ww/v, fwyjwi" 

of the relative frequency of physical defects among, diil- 

''-'- ^^.-^^i^^ '* +>.. "^" -'>-' -rt -www^'^r'^'W' v>,#" t -~mtiti9vr 

A total of 3304 schoolchildren between the ages of 10 and 14 
were classified into dull, normal, and bright groups on the 
basis of school progress. The percentage of children in each 
category having various common defects is shown below (i, 
p, 74). The percentage having any defect at all, as well as 
the average number of defects per child, are also given. 

1 Section on cranial measurements. 


Nature of Defect 





Enlarged glands 




Defective vision 




Defective breathing 




Defective teeth 




Hypertrophied tonsils 








Other defects 








Average number of defects 

per child 




With only one exception every comparison reveals a 
consistent decrease in frequency of defects from the dull 
to the normal and from the normal to the bright group. 
The one exception is defective vision which shows the 
opposite relationship from all the other defects, being 
most frequent among the bright and least frequent among 
the dull subjects. The greater studiousness of the academ- 
ically superior child may be more conducive to eye-strain 
and thus account for this inconsistency, perhaps the most 
noteworthy finding of this investigation is the extremely" 
low degree of relationship indicated between physical de- 
fect and scholastic achievement. 

" Little or no relationship has been found between mental 
traits and such conditions.^ ^general health and mal- 
nutrition. This problem has been very extensively in- 
vestigated in England by Pearson and his students, with 
Consistently negative results. Correiatieae^etwsen, .these 
general physical conditions,, and mtij^ on 

schoolchildren in various social and ecoiioiuic_kvels ^ in- 
V S!SMZ Pf 9 - ec ^ * k^ .'.veiy- close, to-zero. 1 In this country, 
Hoefer and Hardy (10) conducted an intensive investiga- 
tion on 343 third and fourth grade schoolchildren between 
the ages of 8 and II. All the children were American-born 

l Cf., e.g., Pearson and Moull (18). 


Whites; none was feebleminded and none physically de- 
formed. Thus the influence of extraneous factors was 
considerably reduced. Yearly measurements were made 
on the subjects over a period of three years. At these 
times, each child was examined by a physician, anthropo- 
metric measurements were taken, and finally the Stanford- 
Binet and the Stanford Achievement Test in school sub- 
jects were administered. Below will be found the major 
data relevant to the problem under consideration. 


s> j or 7 /- j- - Number Initial Monthly 

General Physical Condition: QJ Cases JQ ^ / 


1. Good 145 104 1.30 

2. Improved 131 105 1.25 

3. Poorer 27 99 1. 12 

4. Poor or fair 40 101 i.n 
Condition of Tonsils: 

1. Tonsillectomy before initial test 78 107 1.28 

2. Tonsillectomy after initial test 64 104 1.33 

3. Normal tonsils 53 103 1.20 

4. Improved tonsils 30 102 1. 20 

5. Diseased tonsils 118 102 1.19 

The children were classified into four groups on the basis 
of general health as determined by the physician. This 
classification was made in terms of the relative condition 
at the beginning and end of the experiment. Thus "good" 
physical condition means "good" both at initial and final 
examination; "improved" and "poorer" indicate the di- 
rection of change; and "poor or fair" refers again to an 
unchanged condition on both occasions. The subjects 
were also divided into five groups on the basis of the con- 
dition of their tonsils, as indicated. In each case, the 
average initial I.Q. of the group is given, as well as the 
average monthly gain in mental age months during the 
experimental period. The intellectual differences among 


the groups are in all cases too small to be of much sig- 
nificance, and the relative status of the physically better 
and poorer groups is often inconsistent with expectation. 

In view of the frequent exaggerated claims made for 
the effect of diseased tonsils upon intellectual status, a 
direct and well controlled investigation of this specific 
problem was conducted by Rogers (24). The subjects 
included 530 public school boys between the ages of 6 
and 14. All had been given the Stanford-Binet as a part 
of the regular school routine. On the basis of an examina- 
tion by the school nurse or physician, the children were 
classified into two groups, the one composed of 236 boys 
whose tonsils were sufficiently diseased to require treat- 
ment, and the other of 294 boys whose tonsils were either 
not defective or so slightly defective as not to deserve 
treatment. The Average I.Q's of the normal and defective 
groups proved tp be 954. and 94.9, respectively. The per- 
centage distribution of the two groups is given in Fig- 
ure 35. The practically complete overlapping of these 
groups is apparent from an examination of the distribu- 
tion curves. 

In order further to check upon any possible influence of 
tonsillar condition upon mental development, 28 boys 
whose tonsils were subsequently removed were retested 
with the Stanford-Binet after a six months' interval. The 
gain in LQ. made by this group was compared with that 
of a control group of 28 boys who suffered from diseased 
tonsils but who had not been operated upon. The operated 
group made an average gain of 2.25 LQ. points as com- 

Siw,i,**Au-*l- ,u, ,,,,, ' '" > -.'' , ','>(,, ,,<?>, ^,]~ 3 l i , ,i ' i,,, , ,,*. <-V >,, 

pared[ to an average gain of 3.28 in the control group. 
Finally, it was possible to test 21 subjects after an interval 
of from 10 to 17 months following the operation. The 
average jgainjft. l,Q.. t ff&&&ky , tH^,gmWR^as,, ,3*0 .points, 
while a control group of 21 cases^gained 6.2 points. It is 











70- 80- 90- 100- 
80 90 100 110 
Intelligence Quotient 

AND DISEASED TONSILS. (Data from Rogers, 24, p. 29.) 

very doubtful whether further retests after a longer delay 
would reveal any effect of the tonsillectomy on intellectual 
development, , Jifejj^k^^ 

ity of th^defcctive group as cempamd* ta.the|]iprmal 
group at the outset and the absewe pi 4UyllIlpJpvement 
in I.Q. which could be directly attributed to the., removal 
oF^SIs^seH tonsils are inutually,cpi:i:obQ,r^tiY^in , deuion- 
stfatmg a lack of relationship between ment^Ul -lewl and 
this "particular physical condition. 


t|me in the popular press i and 

effects oTHenf alvearies (decayed, t 

tions. Although there is relatively; litjlp^i^forniation on 

this question, what there is seems to point to a complete 


lack of relationship. Pearson and Moull (18), for example, 
report a correlation l of .15 between number of carious 
teeth and estimates of intelligence on a group of 617 
Jewish boys and a similar correlation of .10 on 581 Jewish 
girls living in London. 

A rather .suggestive study on this problem was con- 
ducted by Kohnky (13). Two fifth grade classes in the 
same school, closely similar in all respects, were selected 
for the experiment. One class, consisting of 38 children, 
served as the control group. The other, comprising 40 
children, received all possible dental attention during the 
school year. This included dental treatment whenever 
needed, toothbrush drills, dinners to afford opportunity 
to teach proper mastication, inspection by the school 
nurse, home visits by a social worker, etc. A^ series of 
sen^ori-mqtor and simple mental tests were administered 
to both groups in October and in May. The differences in 
gain made by the control and experimental groups were 
very slight and inconsistent, in a few cases the control 
group making the larger gain. 

It is commonly believed that hookworm (Necator amer- 
icanus) infection produces mental defect, sluggishness, and 
apathy. Because of the very common occurrence of this 
infection among schoolchildren in certain parts of the 
country, it has attracted the attention of educators. 
Several studies have indicated a tendency for children 
with hookworm infection to be duller than those not so 
afflicted. An investigation by Smillie and Spencer (26) 
gives typical results. A group of 118 children in grades 
3 to 7 of three rural schools in a hookworm "area" were 
given the Otis Intelligence Test. Their scores were trans- 

1 The two variables correlated in this study were so arranged that a positive 
correlation would indicate more carious teeth among the less intelligent in- 


muted into I.Q.'s in order to eliminate the disturbing 
factor of age. On the basis of medical tests, it was possible 
also to determine the degree of hookworm infestation for 
each child. Below are given the average I.Q.'s of children 
in five categories, ranging from a normal group who showed 
no trace of hookworm infection to the most heavily in- 
fected group (from 26, p. 319). 

Intensity of Infection Number of Cases Average I.Q. 

Normal 17 90.2 

Very light (1-25) l 40 88.3 

Light (26-100) 27 86.4 

Moderate (101-500) 23 84.1 

Heavy (501-2000) 10 76.3 

Although the differences in averages are appreciable if 
extreme groups are compared, the overlapping of all 
groups is large. When individual scores rather than group 
averages are considered, a correlation of .30 2 is obtained 
between LQ. and degree of hookworm infestation. 

This correlation, although not high, indicates a some- 
what closer degree of relationship than has been found 
between mental level and any of the other physiological 
conditions so far discussed. The^ analysis of results ob- 
tained in investigations on hookworm suggests the ppera- 
tioEToFa factor whack is probably pre^eat^ -^Ithougk to a 
lesser extent, in all studies on the i-elatipnahip w between 
mental and physical characteristics. The individuals of 
inferior physical condition in general tend to come, from a 
poorer social level: their environment is deficient in op- 

T. ,, ..-.. " ">< * ,,,,?., i ' i .,. , - ,.,.. f ',.-^,,44r>-"^*'miArx/f A 

portunity for mental developI^e^t.a 

conditions, facilities for medical at 

and home ? care, J'ancf sp^fprtti. This is particularly well 

illustrated by hookworm, a condition which is prevalent 

1 Estimated number of hookworms. 

2 Computed by Paterson (16, p. 196), from the data of Smillie and Spencer. 


among individuals of low social status and flourishes In 
very poor and backward rural districts. The environmen- 
tal background may be the common underlying factor 
which leads both to the physical and to the mental con- 
ditions. This could in itself account for what little rela- 
tionship is found between physical condition and mental 


Finally, we may inquire into the effects of sensory defi- 
ciencies upon behavioral development. Visual and audi- 
tory defects are the most serious sensory handicaps for 
man. Since our culture is built to such an enormous 
jextmt upXMX- a fpup3SJo5ij5i"J.aDigaage, and the latter is 
Acquired chiefly. through the eye and the ear y the signifi- 
cance of deficiencies-, in these- particular sensory fields is 
apparent. Sensory limitations have a much more direct 
bearing upon behavior than the other kinds of physical 
deficiency discussed above. -Environmental stimulation 
is cut off by blindness or deafness; the individual so 
afflicted is psychologically "isolated" from cultural con- 
tacts in the same sense as the wolf children of India or 
Kaspar Hauser, described in Chapter III. We should 
therefore expect a fairly pronounced behavioral deficiency 
to be associated with such sensory defects. 

Relatively little progress has been made in the psy- 
chological testing of the blind. 1 Hayes (9) has adapted 
the Stanford-Binet for testing the blind and has also 
administered several group intelligence and educational 
achievement tests to blind subjects, 
chMrgn_L est below the normsfor 

sion; their average LQ. has been estimated a 
aT~compareH to 100 for children in general. A much 

' and Haine7(8)7 " 


greater percentage of children classified as distinctly 
feebleminded are also found among the blind. There seems 
to be no evidence for the popular belief that the blind 
have a finer discrimination than the normal in other 
senses, such as hearing or touch. The remarkable feats 
often accomplished by blind persons through the use of 
other senses result from a more efficient use of sensory 
cues rather than in a superiority of the senses themselves. 
Through prolonged training, an individual may acquire 
the ability to respond to very slight cues which are ordi- 
narily ignored. Such seems to be the case among the blind. 
Minor visual defects seem to have little or no effect upon 
intellectual development. It will be recalled that in Ayres' 
survey, for example, the percentage of visual defects was 
slightly larger among the accelerated and slightly smaller 
among the retarded children than among children of 
normal age-grade location. It should be noted, however, 
that unlike deficiencies in other sensory fields, visual de- 
fects are frequently corrected by the use of lenses. If the- 
child wears glasses from a very early age, the stimulational 
handicap resulting from his sensory deficiency will be 
eliminated. If the relation between sensory defect and 
intellectual development is attributable entirely to the 
psychological "isolation" produced by sensory limita- 
tions, we should not expect to find any mental inferiority 
when the sensory deficiency has been compensated by 
artificial means. 


This is very likely owing to their greater difficulty in the 
acquisition of language. The language ability of the deaf 
in general has been found to be very deficient, and as a 
result their whole educational progress is much slower. 
Even when oral instructions are eliminated, the deaf can- 


not be tested by means of the ordinary intelligence tests 
because of their serious language handicap. 

Reamer (22), for example, reports an average retarda- 
tion of five years in standardized educational tests among 
deaf children. Pintner (^^jjajaj^^ 

deaf,JpQund aja equally .wide discrepancy between the, edu- 
cational achievement of deaf and hearing children. Com- 
paring the performance of deaf children at different ages 
with norms on hearing children, he obtained the following: 

Age P Average Score ^ Educational Quotient 

Expressed as an" Educat-i onal Age 

iz 7 years~9 months 65 

13 8 years- 1 month 62 

14 8 years-9 months 63 

15 9 years 60 

Thus, the average 1 5-year-old deaf subject made a score 
equivalent to that of the average g-year-old hearing child, 
and so on for the other ages. The educational quotient 
given in the third column is to be interpreted analogously 
to the I.Q. 

In the same investigation it was found that the con- 
genitally deaf or those who became deaf during the first 
few years of life manifested greater educational retarda- 
tion than those who acquired deafness later in life, the 
most marked differences being observed between the 
three-year and the five-year groups. Those subjects in 
whom the onset of deafness was postponed until the fifth 
year had had an opportunity to attain a certain level of 
linguistic development before the necessary stimulation 
was cut off. 

In the effort to rule out language handicap, specially 
devised performance and non-language tests have been 
employed with deaf children. In one very comprehensive 
investigation by Pintner (19), a total 0^4432 children, 12 


years of age or older, were tested in 41 schools for the deaf 
by means of the Binixi^^ Test. This test 

involves no language in any part, the directions being 
given by demonstration and pantomime. The average 
score made by children in each age group was transmuted 
into a mental age and from these, I.Q.'s were computed. 
The results are summarized below: 

Age Average M.A. Average l.Q. 

12 10 years 83 

13 10 years-6 months 81 

14 ii years 79 

15 12 years 80 

If these averages be compared to those obtained with 
educational tests (cf. above), the greater inferiority on the 
latter will be apparent. The^lisiination^of even written 
language from, the test situation has reduced the handicap 
of the deaf child, but it has not eliminated it. By cutting 
off an important source of environmental stimulation, 
deafness has produced a more widespread effect than just 
a linguistic deficiency. The subject is backward in all 
intellectual tasks, whatever their nature. 

Mention should also be made of the deaf-mute. These 
individuals present a very striking illustration of the in- 
fluence of environmental stimulation in the development 
of a function. Never having heard the human voice, the 
deaf-mute is unable to speak although his vocal organs may 
be perfectly normal. The presence of human vocal organs 
does not in itself lead to the development of human speech, 
any more than any other structure insures the presence of 
the function ordinarily associated with it. Vocal organs 
of a certain type are a necessary but not a sufficient con- 
dition for the acquisition of speech. That the deficiency of 
the deaf-mute is a stimulational one is demonstrated by 
the cases in which such persons have been taught to speak 


through the use of other cues. The remarkable results 
obtained in a few such cases, of which the blind deaf-mute 
Helen Keller is probably the most famous example, again 
testify to the importance of training in behavioral de- 
velopment. When even such intense structural handicaps 
as complete blindness and deafness have been overcome 
by intensive training to such an extent that the individual 
is capable of normal or even superior intellectual achieve- 
ment, the factor of structural limitation seems to lose 
much of its potency. 

In regard to milder hearing deficiencies, there is some 
evidence to suggest a possible effect upon intellectual 
status. Sterling and Bell (28) tested 1860 schoolchildren 
between the ages of 8 and 17 with an audiometer. 1 Having 
arbitrarily defined a "significant loss of hearing" as a loss 
of nine or more units from the average reading on the 
audiometer scale, these investigators found such a hearing 
deficiency among 2.9% of the retarded children and only 
1.2% of those in the normal age-grade location. Similarly, 
when the children were divided into those doing excellent 
school work, those whose work was satisfactory, and those 
whose work was unsatisfactory, the percentage of children 
with hearing deficiency in each group was 1.6, 1.7, and 
2.2, respectively. I.Q.'s were available on 585 of the total 
group of children. When these subjects were classified on 
the basis of intelligence test performance, the following 
results were obtained : 

,. ft Percentage of Children Showing 

a Significant Loss of Hearing 

Above average 0.6 

Normal 1.6 

Below average 3.7 

1 A very accurate standardized instrument for determining the weakest, or 
least intense, audible sound for each ear. 


Although very small, these differences are interesting in 
view of the fact that the hearing deficiencies under con- 
sideration were not so serious as to produce a marked 
stirnulational handicap. 


In the light of the various findings on the relationship 
between jnental and physical traits which have been sur- 
veyed in the preceding sections, we may inquire into the 
pO4]bj natnt^oi such a relationship. We are confronted 
in the first place with certain abnormal conditions of the 
organism which have characteristic physical as well as 
behavioral symptoms. It is unwarranted, however, to 
generalize from the association found in such pathological 
cases to a possible connection among individuals in gen- 
eral. To take an obvious and extreme illustration, an 
individual whose legs have been amputated to the knee is 
unable to dance; we cannot conclude from this, however, 
that length of leg is correlated with dancing ability and 
that those persons with longer legs will be the better 
dancers within a group. 

^ ,d.emon- 

^ iittle^is 


ingjthe qperation rti ^ in -behavioral 

development. In the field of endocrinology, for example, 
much remains to be learned. Too often what has been 
offered as a stimulating hypothesis for further research 
has been interpreted by the layman as an established fact. 
The same may be said in regard to nerve physiology. The 
field abounds in speculation and the experts still disagree. 
At such a stage, it is definitely premature to venture a 
systematic analysis of behavior in terms of the nervous 


If we turn from the observation of pathological cases 
and speculations on the physiological mechanisms under- 
lying behavior to data collected on normal groups, we 
still meet difficulties. Many of the investigations on this 
problem have been inadequately controlled. Through the 
misinterpretation of statistical techniques, slight general 
trends in groups have been erroneously attributed to 
individual cases. It will be recalled, for example, that the 
small differences in group averages, which were regarded 
as significant by many early workers, actually showed 
only a negligible relationship when the individual scores 
were correlated. Tli^J^r^ groups 

was pften_ig|XQ.lfid- Age differences were occasionally 
pTesent within the groups, thus producing a spurious con- 
nection between certain physical characteristics and men- 
tal level. 


utmost impprtance,Jn (( ,a J liy i^ye?.t:ig^tiQA. H pa ^.J^l^lP^'- 
s^ of jphysical and .mental condition. The individual of 
superior social level, coming from a better home, will have 
richer opportunities for intellectual development and at 
the same time receive better physical care. He will be 
brought up under more sanitary conditions and will have 
less chance of contracting disease than the less fortunate 
child reared in a city slum or a poor rural district. Tins 
factor is probably responsibly .to a large -extent J^jyh at 
little positive correlation has been found between, mental 
an^physical traits. 

BearingTn inind the fact that direct investigation on 
normal groups has generally yielded very low positive 
correlations between mental and physical characteristics 
and that this correlation would be still further reduced 
if social status were held constant, we shall examine two 
possible interpretations of such a relationship. On the 


one hand we have the theory voiced by Qalton and others 
in the attempt to refute th.e popular, notion of "compen- 
sation." This theory interprets the positive correlation 
between mental and physical traits in terms of some 
general quality of the organism which underlies,, all forms 
of development. It^ssumes_tha,t " good things go to- 
gether" just on general principle, 

tends to be superior in others 


on the, direct 
pS& This 

handicap can take many forms. In the case of sensory 
deficiencies, there is a partial stimulational isolation of 
the individual. Malnutrition, poor health, and other 
general physiological conditions reduce endurance, increase 
fatiguability, affect muscular development, and generally 
lower the efficiency of work. These conditions, if suf- 

^^ -a, certain , ,eztent. Physical defects 

or discomforts also prove a powerful distraction and would 
thus make it more difficult for the child to concentrate 
on his school work or other tasks. Finally, certain strik- 
ing facial, cranial, or bodily characteristics which have 
acquired a specific significance through some traditional 
belief or superstition may affect the individual's subse- 
quent intellectual and emotional development, because of 
the social attitudes which they engender. 


on the 

basis of direct b^vjpiaLluadicap. There is no need to. 
invoEe^TlJoysterious underlying quality which produces 
the all-around "good" person or the all-around deficient 



1. Ayres, L. P. "The Effect of Physical Defects on School 
Progress," PsychoL Clinic, 1909-10, 3, 71-77. 

2. Brooks, F. D. "The Organization of Mental and Physical 
Traits during Adolescence," /. Appl. PsychoL, 1928, 12, 

3. Evans, A. L. The Alleged Relations between the Face and the 
Character. Unpub. A.B. Thesis, Univ. Wisconsin, 1921 
(also reported in Hull, 12). 

4. Fowler, 0. S. Human Science or Phrenology. Phila.: Nat. 
Pub. Co., 1873. Pp. 1211. 

5. Galton, F. Hereditary Genius. London: Macmillan, 1914. 
Pp- 379- 

6. Gates, A. I. "The Nature and Educational Significance of 
Physical Status and of Mental, Physiological, Social, and 
Emotional Maturity," /. Educ. PsychoL, 1924, 15, 329-358. 

7. Goddard, H. H. "The Height and Weight of Feebleminded 
Children in American Institutions," /. Nerv. and Mental 
Diseases, 1912, 39, 217-235. 

8. Haines, T. H. "Mental Measurements of the Blind," 
PsychoL Hon., 1916, No. I. Pp. 86. 

9. Hayes, S. P. Terman's Condensed Guide for the Stanford 
Revision Adapted for the Blind. Watertown, Mass.: Perkins 
Inst. for the Blind, 1930. 

10. Hoefer, C, and Hardy, M. C. "The Influence of Improve- 
ment in Physical Condition on Intelligence and Educational 
Achievement," 2jth Yearbook, Nat. Soc. Stud. Educ., 1928, 
Parti, 371-387. 

11. Hollingworth, L. S. Gifted Children, Their Nature and Nur- 
ture. N. Y. : Macmillan, 1926. Pp. 374. 

12. Hull, C. L. Aptitude Testing. Yonkers-on-Hudson: World 
Book Co., 1928. Pp. 535. 

13. Kohnky, E. "Preliminary Study of the Effect of Dental 
Treatment upon the Physical and Mental Efficiency of 
Schoolchildren," /. Educ. PsychoL, 1913, 4, 571-578. 

14. Murdock, K., and Sullivan, L. R. "A Contribution to the 


Study of Mental and Physical Measurements in Normal 
Children/' Amer. Phys. Educ. Rev., 1923, 28, 209-215; 
276-280; 328-330. 

15. Nors worthy, N. "The Psychology of Mentally Deficient 
Children," Arch. PsychoL, 1906, No. I. Pp. in. 

16. Paterson, D. G. Physique and Intellect. N. Y.: Century, 
1930. Pp. 304. 

17. Pearson, K. "Relationship of Intelligence to Size and 
Shape of the Head and Other Mental and Physical Char- 
acters," Biom., 1906, 5, 105-146. 

1 8. Pearson, K., and Moull, M. "The Problem of Alien Im- 
migration into Great Britain, Illustrated by an Examination 
of Russian and Polish Jewish Children," Part II, Ann. 
Eugenics ', 1925-26, I, 56-127. 

19. Pintner, R. "A Mental Survey of the Deaf," /. Educ. 
Psychol., 1928, 19, 145-151. 

20. . Intelligence Testing: Methods and Results. N. Y.: 

Holt, 1931. Pp. 555. 

21. Porteus, S. D., and Berry, R. J. A. "Intelligence and Social 
Valuation, a Practical Method for the Diagnosis of Mental 
Deficiency and Other Forms of Social Inefficiency," Fine- 
land Training Sch. Res. Pub., No. 20, 1920. Pp. 100. 

22. Reamer, J. C. "Mental and Educational Measurements of 
the Deaf," Psychol. Man., 1921, 29, No. 3. Pp. 130. 

23. Reid, R. W., and Mulligan, J. H. "Relation of Cranial 
Capacity to Intelligence," /. Roy. Anthr. Inst., 1923, 53, 

24. Rogers, M. C. "Adenoids and Diseased Tonsils, Their 
Effect on General Intelligence," Arch. Psychol., 1922, No. 50. 
Pp. 70. 

25. Sherman, E. B. An Experimental Investigation concerning 
Possible Correlation between Certain Head Measurements and 
University Grades. Unpub. A.B. Thesis, Univ. Wisconsin, 
1923 (also reported in Hull, 12). 

26. Smillie, W. G., and Spencer, C. R. "Mental Retardation in 
School Children Infested with Hookworms," /. Educ. 
Psychol., 1926, 17, 314-321. 


27. Sommerville, R. C. "Physical, Motor, and Sensory Traits," 
Arch. PsychoL, 1924, No. 75. Pp. 108. 

28. Sterling, E. B., and Bell, E. "Hearing of School Children 
as Measured by the Audiometer and as Related to School 
Work," U. S. Public Health Reports, U. S. Health Service, 
1930,45, 1117-1130. 

29. Terman, L. M. Genetic Studies of Genius. Stanford Univ. 7 
Calif.: Stanford Univ. Press, 1925. Vol. I. Pp. 648. 


The relationship between mental and physical traits 
has also been considered from the point of view of con- 
stitutional types. In the effort to simplify the almost infinite 
observable variations among individuals, certain basic 
human types have been proposed. A specific individual 
can then be described as a more or less close approxima- 
tion to one of a small number of types. Such constitu- 
tional types are offered as a characterization of the indi- 
vidual as a whole, in all his physical, intellectual, and 
emotional traits, and are not to be envisaged in terms of 
any isolated qualities of the organism. Tl^i^-4s-~alsaa 

innate ,or,, Jxereditary, ba,sis to 

the,.jdevelopment,aLj:jpes. TliusjyJ^ constitutional 

degree of conformity among the 

various characteristics, of ,/the individual, these character- 
istics beiEtg ultimately attributed to aa underlying innate 
tendency. 1 

***W**i!i>*W ,.^, 

Type theories have been eagerly seized upon by the 
general public as a short-cut to the understanding of 
human nature. The layman is impatient with the slow, 
meticulous methods of science. This is particularly true 
in psychology, because of the more intimate and immedi- 
ate bearing which this science has upon man's everyday 
life. The terminology of type theories has become such 

1 The concept of types has also been employed in the description of specific 
functions, as in Galton's classification of individuals in regard to their pre- 
dominant field of imagery, i.e., visual, auditory, olfactory, etc. (3). Such types, 
however, do not characterize the personality as a whole, and are not to be con- 
fused with the constitutional biotypes under consideration. 



an integral part of our language that it is almost impos- 
sible for us to speak about people without reference to 
some hypothetical categories. Sooner or later we inad- 
vertently lapse into this practice. The popular tendency 
to make sharp distinctions, together with the previously 
discussed efforts to "read" character and mentality from 
physical signs, has done much to keep " types" alive. 

In view of their wide and persistent practical influence, 
type theories should be closely examined and submitted 
to experimental analysis. Recently there has been a 
revival of interest in the problem of constitutional types 
among psychologists. In the present chapter, we shall 
survey briefly some of the best-known type theories, 
inquire into their psychological implications, and exam- 
ine some representative data collected to support or test 
their claims. 


The first clearly formulated attempt to classify indi- 
viduals into basic types was probably that of the Greek 

the fifth century B.C. Hippoc- 

rates proposed a two-fold division into habitus apoplecti- 
cus and habitus phthisicus. The former corresponds to a 
thick-set, heavy body build, susceptible to apoplexy and 
similar physical disorders; the latter is characterized by a 
long, slender body and susceptibility to respiratory dis- 
eases such as tuberculosis. Because of the predominantly 
medical interest of its exponent, this classification was 
based primarily upon relative susceptibility to different 
kinds of physical ailments. Sudh^jaiLJ^tpiXia^ 
ever,. persisted to,ihe piesmt^joaanyxurj^^ 
taking, susceptibility ,to ^various JD^ 

The second century Greek physician Galen, frequently 


called the father of modern medicine, is reSBQfidlslsJfor 
jthe jjrdl-J|:j3OT into the 

e .choleric^ ,the^pjblegia"ti% and the melan- 

cholic. These terms have achieved great popularity as 
descriptive figures of speech, although one wonders how 
often they are still being taken literally. Tig theories of 
bothJHippocrates ,,.and ,Galea, 4 ,wer,e, , founded upon.a ( Jbio- 
ch^icaJ^jp^roach^ to personality. Thus Hippocrates 
attributed the development of his two types to the rela- 
tive proportion of "fire" and "water" elements in the 
individual's make-up. Jo^deiLJ^ 


Passing to more modern times, we find a wide variety 
of type concepts in literature, art, philosophy, medicine, 
anthropology, or any other field in which man is the 
central figure. The English anthropologist Walker, 1 in 
1852, wrote of "nutritive beauty," "locomotive beauty," 
and "mental beauty." In the following year, Carus, 1 
a German zoologist, described three bodily types. These 
were the phlegmatic, in whom the region of the digestive 
organs is prominent, the athletic, with strongly developed 
bones and muscles, and the asthenic, with narrow chest, 
a long body, and poorly developed skeleton and muscula- 
ture. In France, several type theories have been pro- 
posed, chief among which is that of Sigaud 1 and his 
students. Sigaud recognized four types, which he desig- 
nated the digestive, the muscular, the respiratory, and 
the cerebral. Manouvrier l suggested a division into 
makroskele and brachyskele, or narrow skeleton and broad 
skeleton. MacAuliffe 1 offered the type plat (flat) and the 
type rond (round). 

In Italy, Viola (cf. 19) formulated a theory which has 

1 Cf. Wertheimer and Hesketh (28). 


become familiar to psychologists through the researches 
of Naccarati (19, 20, 21) and others in America. Viola's 
types include the macrosplanchnic, the normosplanchnic, 
and the microsplanchnic. The macrosplanchnic individual 
possesses a large trunk which is excessively developed in 
comparison with the length of the limbs; in such a body 
type, the horizontal dimensions are relatively large, the 
vertical relatively small The microsplanchnic, on the 
other hand, has a small trunk and long limbs, the vertical 
dimensions being relatively in excess of the horizontal. 
Between these two extremes is the normosplanchnic, who 
exhibits a proportionate and harmonious development of 
trunk and limbs. Viola suggested a series of body meas- 
urements to be employed in classifying individuals into 
these types. Naccarati (19) subsequently devised a mor- 
phologic index as a single numerical expression of body 
build. This index is computed as follows : 

f one arm + length of one leg 

Ayr T 

volume of trunk 

The trunk volume is determined by a series of rather 
elaborate measurements. 

According to Viola's theory, the macrosplanchnic rep- 
resents an overdevelopment of the nutritional or "vegeta- 
tive system" contained within the trunk. The micro- 
splanchnic, on the other hand, is characterized by an 
overdevelopment of the "animal system," consisting of 
the musculature, nervous system, and skeleton. Intel- 
lectual and emotional differences are attributed to the two 
types, because of the relative activity of the vegetative 
and animal systems which are regarded as independ- 
ent and even antagonistic in their action. The macro- 
splanchnic is regarded as representing a lower evolution- 
ary level than the microsplanchnic because of the greater 


morphologic resemblance of the former to the newborn 
and of the latter to the adult. Naccarati (19), in his 
elaboration of Viola's theory, also suggests that the micro- 
splanchnic corresponds to a hyperthyroid condition and 
should therefore be expected to manifest the various 
characteristics associated with overactivity of this gland. 

Pende (cf. 28) has more recently proposed a classifica- 
tion into hypervegetative and hypovegetative biotypes, 
which, as the terms imply, has much in common with 
Viola's theory. A definite endocrine basis is offered for 
this theory. 

In America, Davenport (2) has classifi^d w j^ 
into jthe fleshy, the . mediuii^^ 

'Stockard (26) distinguishes between the linear and the 
lateral types, which he ties up with the activity of the 
thyroid. The linear type is described as active, energetic, 
and nervous, but emotionally controlled; such individuals 
grow rapidly and reach puberty at a relatively early age. 
The lateral type is less active and grows at a slower rate. 
The former type of individual is also characterized by a 
dolichocephalic skull, the latter by a brachycephalic one. 
Mention should also be made, from the psychological side, 
of the tiJQaousj^ (8) 


b^anceto thejntro 

..-ot~tiau^^ 0** 

the basis of observations made in the course of his condi- 
tioning experiments on dogs, be^jgroposestv^^gre 

I ntermedi- 
ate, less pronounced types are also described. Pavlov 


points to a resemblance between the classification so 
obtained and the classical division into sanguine, melan- 
cholic, phlegmatic, and choleric temperaments. He sug- 
gests that, "Until a rigid scientific classification is fully 
established for all the various types of central nervous 
system * . * we may be permitted to make use of the 
ancient classification of the so-called temperaments" (22, 
p. 286). 

Type psychology has flourished most vigorously in 
Germany. Numerous variations and ramifications of 
type theory have been formulated by contemporary Ger- 
man psychologists. Weidenreich (27), after a survey of 
the current type psychologies, has attempted to reduce 
all types to two, namely, the leptosome, with long, narrow 
body, and the eurysome, with short, thick-set body. 
(cf . 12, 14) has proposed a classification qf^con- 

stitutional types on the basis^&J.^idrtic,,, imagery. The 
eidetic image is a peculiarly vivid and detailed memory 
image l which is experienced by some individuals. Eidetic 
imagery has been found to be most common in late 
childhood and to disappear gradually during adolescence, 
although it has also been discovered among some adults. 
The eidetic image may be a photographic replica of the 
original object, or it may differ from the latter in certain 
characteristic ways. Jaensch and his co-workers maintain 
that eidetic images are not a pathological phenomenon, 
but represent a normal stage in the development of many 

JaeaadL.iOg^ eidetic individuals. 

In -t4e"~fe^^ be^ca^ 

The eidetic image "In '"sucET cases 

ffi9 re . .jthan a .visualized idea and it is 

1 Eidetic images have usually been investigated in the visual field, although it 
has been claimed that they are equally common in other senses. 


ft^ Individual. , In 

tlxe.jseond-type^ the image,, naually ..arises spontaneously 
and ,miy. persevere in spite, oi, efforts to banish it; volun- 
tary alterations in the qualities of the image are often 
impossible. Such images do not come up very frequently 
and are often regarded as unpleasant and even uncanny 
by the subject. Jaensch considers these two eidetic types distinct constitutional types', "manifested in many 
bodilyLJSSL mental traits,_and characterized by basically 
diflFexejg,l - ",ps,y:chQphysical reaction- systems." The eidetic 
characteristics are simply taken as convenient starting 
points in the classification. Th^-^&^t.-jDf^thjs, two ;types 

of its alleged resemblance to the Basedow ^syndrome, 1 and 
the^ second j some 

of its manifestations to the condition of-tetany. 2 

Jnng!,siatrQv.ert and extrovert tj^pes are well-known (9). 
In the extrovert, the " psychic energy" is turned outward 
to the objective environment. In the introvert, it is 
turned inward to a subjective world. The extrovert is 
predominantly oriented in all his actions, thoughts, inter- 
ests, and feelings, by the objects and people about him. 
His beliefs and opinions are guided by the mores of his 
group. The introvert, on the other hand, is governed by 
subjective factors; all his behavior has a subjective, inner 
reference. Jung regards these two types as fundamental 
biological contrasts. They denote for him basic attitudes 
which characterize all aspects of the individual's psycho- 
logical make-up. 

1 A condition characterized by prominence of the eyeballs > enlargement of the 
thyroid gland, muscular tremors, rapid heart action, and more or less profound 
mental disturbance; believed to be caused by overactivity of the thyroid gland. 

2 A motor disorder, including muscular tremor, muscular spasms, and some- 
times uncoordinated muscular contractions following upon an effort to make a 
voluntary movement; attributed to insufficient secretion of the parathyroid 


Jung's types have become more widely known, how- 
ever, in terms of their emotional and social manifestations. 
Thus the introvert is usually thought of as an emotionally 
shut-in individual who shuns social contacts, prefers to 
work alone, and finds more pleasure in imaginative work 
than in a life of action. The extrovert suggests the 
"salesman" type, who meets people easily, is happiest 
in a social situation, friendly, and interested in his fellow- 
beings. Jung regards introversion and extroversion as 
characterizations of normal people. In extreme forms, 
to be sure, they would predispose the individual to mental 
disorders which are opposite in their symptoms. 1 The 
fundamental distinction, however, is not made on the 
basis of these mental disorders. The susceptibility to one 
or another form of insanity is considered simply one more 
manifestation of the basic type. 

Kretschmer's type theory (15) has probably been the 
most influential in stimulating research. Physically, 
^ individuals into four groups, the 
pmej wd. 4y.splastic. The pyknic 
type of body build is short and thick-set, with relatively 
large trunk and short legs, round chest, rounded shoulders, 
and short hands and feet. The athletic has a more propor- 
tionate development of trunk and limbs, well-developed 
bones and muscles, wide shoulders, and large hands and 
feet. The leptosome is generally characterized by small 
body volume in relation to height. He is tall and slender, 
with relatively narrow chest, long legs, elongated face, 
and long, narrow hands and feet. In the dysplastic cate- 
gory are placed all individuals who present some marked 
abnormality of physical development, disproportion, glan- 

1 This distinction has been stressed by McDougall, who states for example: 
" . . . persons of the extrovert temperament seem more liable, under strain, 
to disorder of the hysteric or dissociative type; those of introvert, or shut-in, 
temperament to disorder of the neurasthenic type" (17, p. 28). 


dular imbalance, or other defect. Kretschmer suggests a 
wide variety of physical measures to be used, in conjunc- 
tion with the clinical diagnosis of the experimenter, in 
differentiating between these bodily types. 

Th^jDaj^^ .Kmtscbmer' 3 theory is th a t 

there exists a jrelatiQushipt between the .body types, which 
rfe opposed " temperarn^nts," 

^ schizoid. The cycloid individual 
manifests personality traits which in extreme cases would 
be classified under the circular, or manic-depressive, form 
of insanity; the schizoid tends toward schizophrenia, or 
dementia praecox. Kretschmer claims that the cycloid 
is usually pykni^jwhereas the TcEzoicT Is leptosome ,pr, 
leslTfrec^^ Although originally applied to 

different forms of mental disorders, this theory has sub- 
sequently been extended to normal individuals who 
manifest no personality disturbance. The terms cyclo- 
thyme and schizothyme have been employed to denote 
these two normal biotypes. The former is described 
as social, friendly, lively, practical, and realistic; the 
latter as quiet and reserved, more solitary, timid, and 
shut-in. It will be noted that these descriptions correspond 
closely to Jung's extrovert and introvert types. 

^ jcajnjietect 

a ggSLdi]2^ 

types. From the standpoint of physique, the distinction 

is one between the long narrow body, with relatively 
long limbs, and the short stocky build, with relatively 
large trunk and short limbs. In respect to personality,, 
we are offered at the one extreme the expansive, sociable, 
easy-going, and practical man, and at the other the more 
taciturn, unsociable, intellectually independent, or ideal- 
istic type. Occasionally, more than two categories are 
given, but the additional types are usually found to be 


either intermediate degrees or modifications of the major 

In some theories, the structural classification is em- 
phasized; in others the behavioral one is foremost. Many 
of the theories draw upon pathological conditions either 
for striking examples or for their starting points, so that 
we frequently find susceptibility to a given class of physi- 
cal or mental disorders as an outstanding characteristic 
of each type. In many cases, too, the various physical 
and personality types have been linked to the problem 
of race and attempts have been made to attribute racial 
differences to the predominance of one or another con- 
stitutional type within each group. Discussion of this 
phase of the problem will be postponed to Chapter XV. 

The concept of types is a broad one. We have been 
here concerned only with theories of constitutional bio- 
types as described in the opening paragraph. For this 
reason, no mention has been made of such theories as 
that of Spranger (25)^ who describes six fundamental 
types of individuality, namely the theoretical man, the 
economic man, the aesthetic man, the social man, the 
man of power, and the religious man. These "types" are 
regarded as meaning-tendencies or values in terms of 
which an individual's responses to his environment are 
to be understood. They are ideal types or schemata of 
understanding, rather than empirically observable bio- 


Type theories have been most commonly criticized 
because of their attempt to classify individuals into 
sharply divided categories. As was pointed out in Chap- 
ter II, such a procedure implies a multi-modal distribution 

1 Cf. also the discussion by Kliiver (13). 


of traits. The introverts, for example, would be expected 
to cluster at one end of the scale, the extroverts at the 
other end, and the point of demarcation between them 
should be clearly apparent. Actual measurement, how- 
ever, reveals a uni-modal distribution of all traits, which 
closely resembles the bell-shaped normal curve. 

Similarly, it is often difficult to classify a given indi- 
vidual definitely into one type or the other. The typol- 
ogists, when confronted with this difficulty, have fre- 
quently proposed intermediate or " mixed" types to bridge 
the gap between the extremes. Thus Jung suggested an 
ambivert type which manifests neither introvert nor ex- 
trovert tendencies to a predominant degree. Observation 
seems to show, however, that the ambivert category is 
the largest, and the decided introverts and extroverts are 
relatively rare. The reader is referred, for example, to the 
distribution curve obtained by Heidbreder with an intro- 
version questionnaire administered to 200 college stu- 
dents (Ch. II). It will be recalled that the majority of 
scores were intermediate and that as the extremes of 
either introversion or extroversion were approached, the 
number of cases became progressively smaller. The curve, 
too, showed no sharp breaks, but only a continuous 
gradation from the mean to the two extremes. As was 
indicated in Chapter II, the same may be said of all other 
measurable traits of the individual, whether social, emo- 
tional, intellectual, or physical. 

It is-^app-a^ei^r^fe^^ 

Such an assumption, however, is not necessarily inherent 
in all systems of human typology. It is more character- 
istic of the popular versions and adaptations of type 
theories than of the original concepts. To be sure, type 


psychologists have often attempted to categorize indi- 
viduals, but this was not an indispensable part of their 
theories; their concepts have occasionally been sufficiently 
modified to admit of a normal distribution of traits. 

Th^, suggestion has been offered that type theories 
may refer simply to varieties or breeds of man, which 
were originally pure "biotypes." Through successive 
generations of interbreeding, mixed types have been pro- 
duced which now outnumber the remaining specimens of 
pure types. It is well known that through the mechanism 
of heredity, interbreeding will in the long run produce a 
larger number of mixed than pure individuals. The same 
applies to interbreeding among the proposed human bio- 
types. This situation would then present a normal dis- 
tribution of traits, with the largest number of individuals 
in the center of the distribution, corresponding to the 
numerically largest "mixed" group. 1 Thus the form of 
the distribution curve cannot in itself indicate the com- 
position of the group. The normal curve might be ob- 
tained with a single intermediate type and minor devia- 
tions from it, or it might result from the mixture of several 
pure biotypes. 

TJie only essential implication in this concept of bio- 
types seems to be a certain organization among the, Car- 
ious characteristics of the individual. Thus a relation- 
ship would be expected between body build, emotional 
reactions, and intellectual traits. If there exist diverse 
biological types of man, each manifesting its own pecu- 
liarities in physique, personality, and intellect, we should 
find a certain degree of conformity among these char- 
acteristics of the individual. Wfeea. &Q,.coacdXQd^,^the 
problem of types is ultimately reducible to a considera- 

1 A particularly lucid statement of this point of view can be found In Klineberg 
etal. (ID).' 


tion of the relationship between .structural and behavioral 
qualities. It is not, however, concerned with isolated 
traits, but with the composite picture of the individual 
as a whole. 

Insofar as the existence of human biotypes 
determined from the form of the distribution curve, the 
question may be raised regarding available techniques of 
typological, investigation. One method involves the classi- 
fication of individuals into distinct groups on the basis of 
personality tendencies, and the subsequent comparison 
of these groups in regard to physique. This technique has 
been employed largely with abnormal cases in the effort 
to check the assertions that a given physique predisposes 
the individual to a certain kind of mental disorder. Thus, 
for example, the relative number of pyknics and lepto- 
somes among individuals manifesting different forms of 
insanity has been compared and evaluated in terms of the 
expected association. 

A second method is based on the correlational analysis 
of measurements collected on large normal groups. Vari- 
ous physical indices of body build have been worked out 
for this purpose. Such indices are then correlated with 
test scores or ratings on crucial personality traits. A 
high correlation would be evidence for the conformity 
implied by type theories. 

Finally, efforts have been made in a few studies to 
identify and select "pure types" and then investigate 
thoroughly the characteristics of these individuals. The 
types are chosen on the basis of physical characteristics, 
so as to represent "good specimens" in this one respect. 
The physically contrasting groups 'are then compared in 
emotional and intellectual reactions. This method rests 
upon two questions. First, can individuals be found who 
correspond to the alleged biotypes in all their physical, 


intellectual, and emotional characteristics? Secondly, 
when persons are put into classes on the basis of clear- 
cut and extreme physical diversities, will they also exhibit 
corresponding differences in other traits? It will be noted 
that the second question is similar to that which underlies 
the study of types among the psychotic and neurotic. 
In the present method, however, the classification is 
employed on normal rather than on pathological cases, 
and physical rather than emotional traits are taken as 
the starting point. Some of the major investigations by 
each method will be surveyed in the following sections. 

Kretschmer originally formulated his theory of consti- 
tutionai types from observations on psychotic patients, 
In comparing the body build of schizophrenics and manic- 
depressives, he has consistently found a greater propor- 
tion of leptosomes among the former and pyknics among 
the latter. Recently Kretschmer (16) has compiled data 
from several investigators on over 4000 abnormal cases, 
with the following results : 

Body Type Schizophrenic Manic-Depressive 

Pyknic and mixed pyknic 12.8% 66.7% 

Leptosome and athletic 66.0 23 .6 

Dysplastic 11.3 -4 

Unclassifiable 9-9 9-3 


.and athletic categories, 

SS^ E centa ? e ^ ,raanic-cl,epressivea fall 


(28) measured 65 male pa- 

tients chosen at random from two American institutions 
for the insane. Of these, n had been clearly diagnosed 


as manic-depressive and 23 as schizophrenics. The major 
part of the investigation was therefore confined to these 
cases. The subjects were first classified into Kretschmer's 
body types on the basis of general observation. A series 
of 53 anthropometric measurements were then taken and 
various bodily indices computed. One of these indices was 
ultimately selected as the most satisfactory l and adopted 
as the chief basis of classification. A close correspondence 

"~^---B U *,HK J.UBHJ./F,." u* JCT,. , , (< , 

was found between the two procedures,. Those individuals 
classified ^ as pyknic by the experimenter's diagnosis invari- 
ably .haAindices under 255; those classified as leptosomes 
had indices over 270. There was no overlapping in the 
indices of these two groups. JBjLeWi^nig^gdjpf classifi- 
catonj_haK,ffifir^ the Dumber pl,d,ecided.,pyknics_or lepto- 
some^was small^j^Q^t ,, individuals f ailing ,iatQ , the r inter- 
mediate^athletic^Qr^mized, groups, a.s would be expected. 

The percentages of persons of each body type found 
in the schizophrenic and manic-depressive groups are 
given below: 

Body Type Schizophrenic Manic-Depressive 

(N = 23) (N n) 

Pyknic 4.3% 45-5% 

Pyknoid 13.0 36.4 

Athletic 26.1 9.0 

Leptosome-athletic-mixed 34.8 o. 

Leptosome 17.4 o. 

Unclear 4.3 9.0 



scatter over a wider variety of body type, but the greatest 

** V "****w*M|M*U^, <>*'* ' a * J **' l ^ l "*' V '''^'' 1 ' r ' ' " 1P '" ''* "-H'l i P/ 'S*W<*4W**1*f* ''* V***' *''' S-El***** 1 "* 1 

,aad athktip, 

, _ IPO X leg length X io 3 


transverse chest diameter X sagittal chest diameter X trunk height 
(cf. 28, p. 415). 


The chief difficulty in interpreting the results of these 
and similar investigations on psychotic cases is inadequate 
control of the age factor. Schizophrenia is more common 
among younger subjects, whereas older people are more 
susceptible to manic-depressive psychoses. It is also a 
well-established fact, which Kretschmer himself recog- 
nizes, that older subjects tend more toward the pyknic 
body build, younger subjects toward the leptosome. To 
be sure, pyknics may be found among young people, 
and leptosomes among older groups; and many individuals 
retain the same type of body build throughout life. But 
the general trend is sufficiently marked to produce" aft 
entirely spurious relationship between body build "and 
psychotic tejidencies. For this reason, it is essential that 
age differences be ruled out in any comparison of the 
body type of different psychotic groups. 

In a recent investigation by Garvey (5), 130 manic- 
depressives and 130 dementia prsecox, or schizophrenic, 
patients were selected so that the two groups would be 
closely matched in age. Only clear cases, classified with 
complete agreement by the hospital staff (not including 
the experimenter), were employed. When the patients 
were divided into heavy and slender types . on the basis 
of n general observation, some evidence was found for 
Kretschmer's claims. The association, however, is re- 
ported as too slight to permit body type to be regarded 
as, diagnostic of psychosis. Extensive physical measure- 
ments were taken and several ratios between horizontal 
and vertical bodily dimensions were computed. All showed 
an almost complete overlapping of the two psychotic groups. 
Not only were the averages closely similar, but the range 
and the general form of the distribution were practically 
identical in the two groups. 

Naccarati (20), in the effort to check upon Viola's 


hypothesis, measured 100 male Italian psychoneurotics 
between the ages of 25 and 40. The number of normo- 
splanchnics is reported as being smaller in this group than 
in normal groups. The neurasthenics had a larger propor- 
tion of microsplanchnics (long, slender type), while macro- 
splanchnics predominated among the "emotional psycho- 
neurotics." Under the latter category Naccarati includes 
cases of hysteria, anxiety neuroses, and traumatic neu- 
roses. Averages of some of the most significant physical 
measurements as well as the average age of the two 
groups are given below. 

Q Morphologic Total Volume Length of * 

Index of Trunk Extremities 

50 Neurasthenics 456.64 3-43 I 33-35 32.16 

50 Emotional psycho- 
neurotics 362.06 37-36 128.80 33-94 

It will be noted that the neurasthenic group has a lower 
average age than the emotional psychoneurotics. This 
might account in part for the greater tendency to micro- 
splanchny among the former. No account is given of the 
method of obtaining or diagnosing the subjects, a fact 
which makes interpretation of the findings difficult. 

Although not dealing with abnormal patients, a subse- 
quent investigation by Naccarati and Garrett (21) may 
be mentioned in this connection. The subjects were 
54 male college students between the ages of 18 and 25. 
The general approach was similar to that of the other 
investigations reported in this section. The subjects 
were classified into three groups on the basis of number 
of neurotic symptoms indicated on the Woodworth Per- 
sonal Data Sheet. 1 The investigators also obtained ratings 

1 The students were also given the Pressy X-O and the Downey Will-Temper- 
ament tests, but the results were difficult to interpret, probably because of the 
inadequacy of these tests when applied to college groups. 


by the class instructor and self-ratings of each student 
on physique (including bearing, apparent health, vigor, 
strength, and endurance), intelligence, emotional stabil- 
ity, and aggressiveness. Morphologic indices were com- 
puted for each subject. The average Woodworth P.D. 
score for each group is shown below, together with the 
averages and S.D.'s of the morphologic indices. It will 
be recalled that a high morphologic index indicates micro- 
splanchny, a low morphologic index macrosplanchny. 

Group I Group II Group III 
(N = 18) (N = 16) (N = 20) 

Woodworth P.D. Score: Average 6.9 14.2 24.8 

Morphologic Index: Average 49&-S 495 - 460.8 

Morphologic Index: S.D. 61.3 57.5 56.0 

It will be noted that group III, composed of the most 
neurotic individuals, has a much lower average morpho- 
logic index than the other two groups. The self-ratings 
and instructors' ratings agreed closely with each other 
and with the test results. The average differences among 
the three groups were slight but in the expected direction. 
Thus, in emotional stability, group I was rated as the most 
stable and group III as the least stable. Similarly, group I 
was rated as most intelligent, group III least intelligent. 
These data seem to support Viola's contentions in a 
general way. The macrosplanchnics appear less intelligent 
and have a more pronounced tendency to neuroticism 
than the microsplanchnics. Several reservations should, 
however, be borne in mind. The groups are small; age 
may have differed appreciably among the three categories; 
and finally, much overlapping in morphologic index k 
indicated by the large S.D.'s. Variations in body build 
within each group were larger than the differences between 
the averages. 


Aj^y_cpmp,i:ehensive investigation on the relationship 
^L^SfJ 1 body $7P5 a ?*d P s 7 c ^otic disposition was recently 
QSS^^ jBur chard (i). A total of 407 male White 
patients from several institutions for the insane were 
selected for the survey. Of these, 125 were clearly diag- 
nosed as schizophrenes by the hospital staff, and 125 as 
manic-depressives. The remaining 157 patients mani- 
fested a variety of psychotic and neurotic conditions and 
were employed as a control group. The subjects in all 
three groups were classified into pyknics, athletics, and 
leptosomes by "general impression." Comparisons were 
also subsequently made in respect to several anthro- 
pometric measures and indices. Only seven dysplastics 
were found in the entire sampling, and these were elim- 
inated from further consideration. All other subjects 
were retained, any intermediate or mixed types being 
assigned to the morphological type which they resembled 
most closely. Below are given the percentages of pyknics, 
athletics, and leptosomes found in the manic-depressive, 
schizophrenic, and control groups, respectively, when 
the "impressionistic" method of classification was em- 

Morphological Type Manic _ Depressives Schizophrenes Control 

Pyknic 63.2 36.3 55.6 

Athletic 8.8 17.7 " 11.3 

Leptosome 28.0 46.0 33.1 

The general to^j^J^ * n agree- 

mu^^pTy. ,Not only are the greatest 
percentage of manic-depressives pyknics, and the greatest 
percentage of schizophrenes leptosomes, but the control 
group occupies a position intermediate between these two 
groups in all percentages. When the schizophrenes and 



manic-depressives are compared in terms of anthropo- 
metric measures, a certain amount of differentiation is 
also revealed. Perfectly reliable differences between the 
averages of the two groups were found in three out of 
nine physical measures and in two out of three bodily 
indices. The overlapping of the groups in all of these 
treasures 3^as nevertheless very large. This is illustrated 
in Figure 36, which shows the frequency distributions on 

Manic -Depressive 

Dementia -Praecox 

130 150 170 190 210 230 250 270 290 310 330 350 370 390 

Index Value 



(After Burchard, I, p. 47,) 

Wertheimer-Hesketh index of body build (cf. above). 
This index yielded the largest differences between the 
two groups. It is apparent that, in spite of the statisti- 
cally significant differences in averages, schizophrenes can 
be found who are much more pyknic than certain manic- 
depressives, and vice versa. 

Even the differences in averages between the two groups 
may be owing to other factors which have not been con- 
trolled. Burchard recognized this difficulty and under- 
took a detailed analysis of his manic-depressive and 
schizophrene groups. In regard to racial and national 
background, occupation, and educational status, no ap- 
preciable or consistent differences could be discovered. 
In age, however, the differences were very large, the aver- 
age ages of schizophrenic, control, and manic-depressive 


groups being 30.97, 42.90, and 49.65 years, respectively. 
Further analysis revealed a definite relationship between 
age and body build. This factor seems to have accounted 
largely, although not entirely, for the group differences 

Since the age factor plays such an important part in 
all studies on constitutional type, we may examine more 
closely Burchard's data on this problem. Below will be 
found the average Wertheimer-Hesketh indices of sub- 
jects falling in successive decades within the entire sam- 
pling as well as within each psychotic group. 

Average Wertheimer-Hesketh Indices 
** e Entire Group Schizophrenes Manic-Depressives Control 

15-19 306,11 297.25 262.66 321.00 

20-29 275.10 279.77 252.00 273.48 

30-39 260.82 272.00 256.33 253.86 

40-49 249.34 252.50 246.52 249.41 

50-59 253.68 277.50 247.29 257.16 

60-69 236.50 243.33 241.67 228.75 

These^jtverag^g^ indicate, - a. . definite -teBdency towards a 
more pyknic^ body build with advancing .age. JJlus, jg, 
sfeH^ within each dis&SJg2^^ the 

Further corroboration of this finding is 
furnished by the correlation of .256 obtained between 
age and index value in the entire sampling. Much of the 
difference observed between the two psychotic groups 
can therefore be attributed to age. It should be noted, 
however, that within each decade the schizophrenes have 
a higher average index than the manic-depressives. To be 
sure, the differences are considerably reduced by ruling 
out age, and the control group no longer retains its inter- 
mediate position, but a certain difference in the expected 
direction remains. Burchard himself is very cautious in 
interpreting these findings, concluding ". . . that age 


is a very important conditioning factor upon the mor- 
phological habitus and that although the type of psy- 
chosis apparently play(s) an important role the relative 
weights of the two factors remain in considerable doubt" 
(i, p. 65). 


It has frequently been objected that one cannot gen- 
eralize from a slight correspondence between body build 
and certain forms of insanity to a relationship between 
personality traits and bodily characteristics of normal 
individuals. The s> conj,p,gjlsan Ht gi , average values, further- 
more, or of the percentage frequency of bodily types 
among; different .groups may exaggerate a very slight 
degree of association. Such comparisons tell us little 
abc^jidiyidual cases. For these reasons, a number of 
investigators have resorted to the correlation coefficient 
to pfitain an exact quantitative measure of the amount of 
relationship within a group. 

The correlation coefficient is affected not only by the 
presence or absence of clear-cut types within a group, but 
also by the degree to which a given typal characteristic 
is exhibited. This method seems to rest upon a slightly 
different principle than that underlying group compari- 
sons. Thus if morphological index were found to corre- 
late highly with intelligence, it would mean not only that 
the clearly microsplanchnic are more intelligent than the 
clearly macrosplanchnic, but also that within the inter- 
vening range, the more microsplanchnic the individual, 
the more intelligent he will be. A lack of relationship 
between intelligence and body build within the inter- 
mediate mixed groups will considerably lower the corre- 
lation which would be obtained if only "pure types" 
were included. 


Naccarati (19) found a correlation of ,356 between 
morphologic index and Thorndike Intelligence Examina- 
tion for High School Graduates within a group of 75 col- 
lege men. In the same study, height-weight ratios l were 
computed for 221 college men ranging in age from 17 
to 22, all of whom had taken the Thorndike test. The 
correlation between this ratio and intelligence proved to 
be .230. 

Ihe^^light positive correlation between height-weight 
ratio and in;^ support the claim 

tha4Jiie.mierQ&pl^^ individual, tends 

to be more intelligent. TtiL-age factor, however, must 
again^be^ considered. Upon further statistical analysis of 

the data, , it wa&.jiijBaz^ of -230 

r&gulled, largely frojr^a negative correlation between weight 
and intelligence ..test, score within this group. 2 The more 
heavily built, stocky iadiYiduals at the age levels under 
consideration tend to be t;he,j9/^r members of the group. 
Sinyjji^ .any one academic 

lev/l^art usn&^ It therefore .seems very 

likely that even the low degree of correspondence found 
between height-weight ratio and intelligence is attributable 
to an uncontrolled age factor and cannot be accepted as 
proof of a relationship between body type and mentality. 
Subsequent investigations by a similar method have 
likewise cast doubt upon Naccarati's conclusions. Heid- 
breder (6) checked Naccarati's hypothesis on a group 
of 1000 White, native-born college freshmen, consisting 
of 500 men and 500 women. Scores on the Minnesota 


1 The height-weight ratio has frequently been substituted for the more elabo- 
rate morphologic index, for the sake of expediency, since the two indices are 
closely related. Naccarati (19), for example, found a correlation of .70 between 
the two in a group of 75 students, and a correlation of .75 in another group of 50. 

2 Subsequently computed by Hull (7, pp. 142-143), from Naccarati's published 


College Ability Tests were correlated with the height- 
weight ratios obtained by careful measurements on each 
subject. This correlation proved to be only .03 in the 
group of men and .04 in the women's group. Similarly, 
the correlation between height-weight ratio and scores 
on each of the five subtests of the intelligence exami- 
nation closely approximated zero, ranging from .07 

Irkljie effort to discover whether the use of the more 
elaborate morphologic index in place of the height-weight 
ratio" "might yield more positive evidence for Naccarati's 
view, Sheldon (23) conducted an elaborate investigation 
on 434 freshman men. All subjects were White; age var- 
ied between 17 and 22. Twelve measurements were 
carefully made on each individual and from them were 
computed the morphologic indices, in the manner de- 
scribed by Naccarati. The- correlation between these 
indices and scores on a common group intelligence test 
^2L59^?^ 'freshmen was .14. Correlations of the morpho- 
logic indeFwitE'eacK'oF'tlie nine subtests in the examina- 
tion ranged from .02 to +.12. These ^findings cor- 
roborate closely those obtained by Heidbreder with the 
heigE-weight ratio. 

^ morphologic .types, Sheldon 

(24) correlated ^morphologic index and^xatings oa .five 
peisoaalityiJrcLlts withia a, group-oi Z5| Jrsshmaa . men. 
Each student was rated by five upperclassmen who be- 
longed to the same fraternity as the subject. The judges 
had thus had considerable opportunity to observe the 
student's everyday behavior in many situations and were 
fairly well qualified to rate him. The consensus of all 
five judges was taken as the final rating for each individual. 
Below will be found the correlations between morphologic 
index and ratings on each trait, 


Correlation with 
Trait Rated Morphologic Index 

Emotional excitability .00 

Aggressiveness .08 

Leadership .14 

Sociability .22 

Perseverance .01 

On the whole, these correlations are too low to indicate 
anji^greciable degree of relationship between bodily type 
aniijgersonalitj traits. The correlations of morphologic in- 
dex with leadership and sociability are, however, sugges- 
tive. These two correlations indicate a tendency for the 
more heavily built individual to be more sociable andjoaore 
6Fa leader. This may again be owing to a disturbing age 
factor, inasmuch as the older individuals within such a 
group might well be expected to manifest these character- 

both intel- 

lectucd jLndjjersonality .traits was conducted by Garjrett 
The subjects were again male college 

freshmen. Morphologic indices were computed with meas- 
urements taken from three standard photographs of each 
subject. These photographs, taken in connection with 
gymnasium routine, showed three different views of the 
individual in the nude. The morphologic indices computed 
from the photographs correlated .81 with height-weight 
ratios obtained from direct measurements on 219 stu- 
dents. On this basis, the authors felt justified in their 
use of the photographs for the sake of expediency. JThe 


the George Washington Social intrfKgSficfe Test, 

with the following results : 

",.,, . ...... -j^jadwiuiuju '<*" '*""' "*" " ' 



, , 


Thorndike Intelligence 


Woodworth P.D. Sheet 
Social Intelligence Test 


r n 
of Cases 



- . . 




Height-Weight Ratio 
(fmn ^^ neasure , 

ments ) 


f n 
of Cases 

_ . . 



f. these ^correlations is sufficiently large to indicate 
a significant degree of relationship,. 


The study of constitutional,, types through the correla- 
tion technique has yielded consistently negative results. 
As_ has already been pointed .put, .however, this may be 
owing to the presence of a predominantly Urge, group of" 
mixed types Jn jrhoja ,iw,,CQ]a^sten^ 

and npLental or emationaL traits isi.lo^.iQvjid. 

It has also been argued 

that even when indices are employed in lieu of isolated 
dimensions, the investigator is not getting a picture of 
the individual's physique in its totality. And the latter 
is essential in any concept of constitutional types. 

Most of the numerous German investigations on types 
have proceeded by selecting good specimens of each type 
on the basis of physical measurements or observations 
and then administering a variety of psychological tests 
to the groups so obtained. By this method, for example, 
the conclusions have been reached that pyknics are 
more distractable than leptosomes, that they have a 
greater perception span, a better incidental memory, re- 
spond "synthetically" rather than "analytically" to a 
difficult perception, are more sensitive to colors than to 


forms, are superior in motor tasks except when these 
require delicacy of movement, and give more extroverted 
responses. These are among the major differences reported 
by German investigators. 1 Relatively little stress is placed 
by the latter upon differences in general intelligence be- 
tween the types. 

Many of these studies are open to serious criticism 
and it is therefore difficult to evaluate their findings. 
The groups employed are frequently small 

arej^eported with no indication of variability^within each 
group or of amount of o^^a^mgbttween g rou P s 4 Q.E an " 
titative data ^e t freguently lacki,iiig and only descriptive 
observations reported. TQ^tfeSiS^ or 

poorh^standardized. The 

chieflyjon the basis .of , physical^ in 

other essentiaL respects. Thus the relative proportion of 
men'^ndjv'omen may not have been constant in all the 
groups. The pyknics, furthermore, may have ,be,en, older 
than the leptosomes, and this age difference could account 
for J^lgbserved psychological differences. Little or no 
attempt has been made to control this factor, in some 
studies the subjects ranging from adolescents to sexage- 
narians. SociaLaJLi*^^ 

affected the results. There is some evidence, for example, 
thaFTeptosoTnes are found more commonly among the 
higher social and educational levels. Since there are also 
intellectual and possibly emotional differences among these 
classes, the factor of social level should be ruled out. 

Mohr and Gundlach (18) conducted an intensive quanti- 
tative investigation on a group of male convicts in the 
Illinois State Prison. A total of 600 men was measured, 
out of which 89 were selected as good representatives of 
leptosome, athletic, and pyknic types. In arriving at this 

1 For a survey of many of these investigations, see Klineberg et al. (10). 


classification, the investigators employed all the anthro- 
pometric measures suggested by Kretschmer, as well as a 
general observational diagnosis of body type. Each sub- 
ject was given the Army Alpha as well as about a dozen 
simple psychological tests suggested by the German work- 
ers as diagnostic of constitutional type. Such tests were 
included as speed of tapping and of writing, visual reac- 
tion t time, cancellation, substitution, color fusion, Ror- 
schatch ink blots, etc. 

A striking difference in average Army Alpha score was 
found among the three groups. This is shown below, together 
with the number of cases in each group and the average ages. 

Body Type Number of Cases Average Age Alsbh S T ^ 

Leptosome 19 28.55 96.5 

Athletic 26 28.65 79-2 

Pyknic 44 34.75 57.9 

The correlation between Army Alpha score and an index 
of body build was found to be .34, which further cor- 
roborates the above results. Although not very high, 
this correlation indicates a significant tendency for the 
tall, slender individuals to obtain higher scores. Similarly, 
in many of the other tests the differences among the 
groups were large enough to be statistically significant. 
It will be noted, however, that there is a marked differ- 
ence in age among the three groups, the pyknics being 
on the average a little over six years older than the 
leptosomes or athletics. In view of the tendency for Army 
Alpha scores to decrease with age (cf. Ch. VII), there- 
fore, the pyknic group would be expected to obtain lower 
scores. The cultural and racial composition of the three 
groups is not stated, and these factors may also account 
for some of the observed differences in test performance. 
More recently, Klineberg, Asch, and Block (10) have 


attempted to compare Kretschmer's body types under 
more rigidly controlled conditions. Thejstudy was limited 
exclusively to college students, so that variations in age 
and in social and educational level were largely reduced. 
The first group was composed of 153 male college stu- 
dents, with an average age of 19 years-9 months. All 
were attending the same institution and were very homo- 
geneous in respect to racial and cultural background. 
The subjects were classified into leptosome and pyknic 
categories on the basis of experimenter's diagnosis as 
well as five indices computed from anthropometric meas- 
urements. Each subject was given the Otis Self-Adminis- 
tering test of intelligence, an emotional adjustment test, 
and a series of six tests designed to measure alleged char- 
acteristics of the two opposed constitutional types. 

It was possible to obtain two groups which were clearly 
differentiated in respect to physique. This is illustrated 
by the frequency distribution curves of the leptosome and 
pyknic groups in Pignet Index, 1 reproduced In Figure 37. 


Pyknic <N= 56) 

Uptosome (N=59) 





l I I I I I I t II 

-15 -10 -50 5 10 15 20 25 30 35 40 

Pignet Index 

PIGNET INDEX. (After Klineberg, Asch, and Block, 10, p. 180.) 

1 Pignet Index = Height (weight + chest circumference). 

NOTE: This formula is printed incorrectly in the study under consideration 
( n, p. 164). We assume this was a misprint, and that the correct formula was 
employed in the computations. 


This index was found to differentiate more clearly between 
the groups than any of the other physical measures em- 
ployed. It will be noted that overlapping is virtually 
absent. In sharp contrast to this distribution is that 
given in Figure 38, which shows the scores of leptosomes 



. Leptosome (N=57) 



z 8 

24 32 40 48 56 64 72 80 

Number of Letters Cancelled 

CANCELLATION. (After Klineberg, Asch, and Block, 10, p. 180.) 

and pyknics in one of the psychological tests, viz., can- 
cellation of letters. In this case, the two groups overlap 
almost completely. Similar results were obtained with 
all of the other tests. ]jEUULJS&$^^ 

tion of measures on no cases confirmed these findings. 
The correlations between physical indices and test scores 
were all close to zero. Intercorrelations of the various 
psychological tests were also negligible. If the under- 
lying conformity implied by type theories were present, 
a fairly close correspondence should have been found 


among the various diagnostic tests. Viewed from any 
angle, the results are completely negative. 

A parallel study was conducted on 79 women students 
in one college, all of whom were between the ages of 16 
and 20. Various physical measures, as well as scores on 
the Scholastic Aptitude Test were already available on 
these subjects. They were given, in addition, an emotional 
adjustment test and three simple tests suggested by the 
German type studies. It proved impossible to classify 
the subjects into bodily types, since all fell within the 
leptosome range. As a result, only the correlation tech- 
nique could be employed. 1 As in the study on men, the 
correlations between test scores and physical indices were 
too low to be of any significance. 

A very thojpiagLiliye^tig^tion of personality traits in 
relation to physical type has recently been conducted J^y 
KlmeB^ Eoky (n). 2 The subjects were 

again students, selected from several colleges in New 
York City and its environs. A total of 200 men and 
229 women were examined. Within each of these groups, 
the subjects who fell in the upper and those who fell in 
the lower 25% of the distribution of Pignet Index were 
selected as leptosomes and pyknics, respectively. This 
gave 50 leptosomes and 50 pyknics among the men, and 
57 leptosomes and 57 pyknics among the women. 

That the groups so obtained were clearly differentiated 


measures and indices fou^dior^allth^subjects. In both 
male and female groups, the differences between lepto- 
somes and pyknics were statistically reliable in all physical 

1 As a subsidiary analysis, the subjects were classified into "leptoid" and 
"less leptoid, " and average scores on these two groups were computed. This 
procedure could not, however, be expected to yield very significant results. 

2 The writer is indebted to Drs. Klineberg, Fjeld, and Foley for making avail- 
able to her the unpublished data of this study. 


measures except standing and sitting height and the 
ratio between these two. Not only were the differences 
between averages very large and reliable in all other 
physical measures or indices, but the ranges showed little 
or no overlapping. In regard to age, the male pyknics 
proved to be slightly older on the average than the lepto- 
somes, the average age of the male leptosomes being 
20.17 years and that of the male pyknics 21.08 years. 
In addition to being very slight, this age difference is 
such as to exaggerate any of the alleged psychological 
differences between leptosomes and pyknics. Hence such 
an age discrepancy loads the dice slightly in favor of 
Kretschmer's hypothesis and would make negative find- 
ings all the more conclusive. Among the females, the 
age difference was negligible, the leptosomes averaging 
19.73 and the pyknics 19.23 years. 

All subjects were given the Bernreuter Personality In- 
ventory, This test was scored with six keys, yielding 
measures of as many different though more or less inter- 
related aspects of personality, viz., neuroticism, self- 
sufficiency, introversion, dominance, self-confidence, and 
sociability. 1 The Allport-Fernon Study of Values was 
also administered. This test is designed to measure the 
relative prominence of six basic interests or motives in 
personality, the theoretical, economic, aesthetic, social, 
political, and religious. As will be noted, this classifica- 
tion is based on Spranger's proposed list of evaluative 
attitudes (cf. above). All subjects were further given a 
specially devised test of suggestibility. In addition, it was 

1 Statistical analysis has recently shown that the Bernreuter test can be re- 
garded as measuring two fundamental, independent traits which have been 
labeled self-confidence and sociability (cf. Flanagan, J. C. Factor Analysis in 
the Study of Personality. Stanford Univ., Calif.: Stanford Univ. Press, 1935. 
Pp. 103). The other four scores, although not mutually independent, were in- 
cluded in this study since they correlate highly with scores on other current 
personality tests and correspond to more familiar psychological terminology. 


possible to administer two other tests to many, but not 
all, individuals. One of these was an honesty test, showing 
the number of times the subject cheated on what seemed 
to be an information test (Mailer Test of Sports and 
Hobbies). The other was a specially constructed per- 
sistence test which measured the length of time the indi- 
vidual worked on an insoluble finger maze before giving up. 

In Table XII will be found the average scores of both 
male and female leptosomes and pyknics on each test. 
Critical ratios are also given to show the reliability of the 
differences between the averages. It will be recalled that 
if the critical ratio has a value of 3 or more, the difference 
is regarded as statistically significant. In interpreting 
the data of Table XII, it should be borne in mind that 
on the Bernreuter test, the positive scores indicate a 
greater degree of the trait named, the negative scores a 
lesser degree. Thus in neuroticism, for example, a higher 
positive score indicates a more neurotic individual, a higher 
negative score a less neurotic individual. In introversion, 
the positive scores indicate a tendency toward introversion 
and the negative scores a tendency toward extroversion. 
The same is true of the other traits; the end of the scale 
corresponding to the positive scores is the one from 
which each test was named. In the Allport-Vernon test, 
the higher scores indicate greater prominence of the partic- 
ular "value" in question. In suggestibility, the higher 
scores show a greater susceptibility to suggestion. In the 
persistence test, likewise, the higher scores show greater 
persistence. On the honesty test, the scores were expressed 
in such a form that the higher values corresponded to the 
more "honest" individual who cheats less often. 

The^data of Table XII are clearly negative as regards 

***i^^^^r^ ttK ^^ i ,f W ^ i ^*., Y . i , -, " -, ** " "'".>*fc" **iWwm.*w, ? ,.,,, % , 

type theories! "jNoiie'bi thjej^^ 

iiT'eitKer niale or fcmeoig.srd.iable. In the male 


groups, the critical ratios range from 0.005 to 2.22; in 
the female groups, the range is from 0.09 to 2.22. None 
of the differences is three or more times as large as its 
standard error. All the obtained differences could there- 
fore have resulted from chance errors of sampling. In 
each sex group, there is only one critical ratio which 
reaches or exceeds a value of 2, and this occurs on a 
different* test in the two cases. In the male group, the 
largest critical ratio was obtained on the honesty test, 
which gave a critical ratio of only 0.25 in the female group. 
Similarly, the largest critical ratio in the female group is 
found with the " social values" score on the Allport- 
Vernon scale and this gives a critical ratio of only 0.39 
in the male group. 

It might also be pointed out that in several comparisons 
the differences between leptosomes and pyknics are con- 
trary to expectation. For example, the male leptosome 
group appears more "sociable" on the Bernreuter and 
seems to have a higher sense of "social value" according 
to the Allport-Vernon scale, than does the male pyknic 
group. The average scores of all the groups, furthermore, 
fall very close to the norms for college men and women 
in general. Finally, the ranges of the leptosome and pyknic 
groups were nearly identical, showing an almost complete 
overlapping of distributions on all personality tests. 

To be perfectly cautious, one might conclude that the 
groblem of constitutional types remains an open question. 
All the Setter controlled studies by any of the three 

<1 -^-*,^ aJ *., fa ,-, U,,!'..,^^ , ,,,< , ... ' , , ' ' " J <*' ' ' , , '"" --'* 

nigthods described afepy^ ,. have^ however, ~ yielded^ ,o ver- 

In those studies which 

have reported positive results, it is a relatively easy 
matter to find uncontrolled factors which could, in them- 
selves, have produced the observed differences in alleged 
typal characteristics. Since the concept of types seems to 




(After Klineberg, Fjeld, and Foley, n) 





(N = S o) 

(N S o) 

Ratio of 



Ratio of 


r. BiNiNeuroti- 








2. B 2 S: Self-suffi- 



+ 29.22 



+ 18.02 


3. B 3 I: Introversion 







4. B 4 D: Dominance 
5. Fid Self-confi- 








- B.S4 

- 8.46 


+ 4.67 



6. F 2 S: Sociability 

+ 1.22 

- 6.66 






Study of Values 

I. Theoretical 







2. Economic 







3. Esthetic 







4. Social 







5. Political 



i. 08 




6. Religious 














Persistence * 







Honesty * 







* Not all subjects were' given these tests. 

have proved unsuccessful in explaining the organization 
of traits within the individual, we may now inquire into 
the latter question from a more empirical viewpoint. 
An analysis of variations within the individual, to be 
discussed in the following chapter, will serve as a back- 
ground for this problem. 



1. Burchard, E. M. L. "Physique and Psychosis: an Analysis 
of the Postulated Relationship between Bodily Constitution 
and Mental Disease Syndrome," Comp. Psychol. Mon., 
1936, 13, No. i, Pp.73- 

2. Davenport, C. B. " Body-Build and Its Inheritance," 
Carnegie lust. Wash. Publ., No. 329, 1923. Pp. 176. 

3. Galton, F. Inquiries into Human Faculty and Its Develop- 
ment. London: Macmillan, 1883. Pp. 387. 

4. Garrett, H. E., and Kellogg, W. N. "The Relation of 
Physical Constitution to General Intelligence, Social In- 
telligence, and Emotional Stability," /. Exper. Psychol., 
1928, u, 113-129. 

5. Garvey, C. R. "Comparative Body Build of Manic- 
Depressive and Schizophrenic Patients," Psychol. ulL, 
*933, 3, 567-568 (see also p. 739). 

6. Heidbreder, E. "Intelligence and the Height- Weight Ra- 
tio," /. Appl. Psychol., 1926, 10, 52-62. 

7. Hull, C. L. Aptitude Testing. N. Y.: World Book Co., 1928. 
Pp. 535- 

8. James, W. Pragmatism, a New Name for Some Old Ways 
of Thinking. N. Y.: Longmans, 1907. Pp. 309. 

9. Jung, C. G. Psychological Types (transl. by H. G. Baynes). 
N. Y.: Harcourt, Brace, 1924. Pp. 654. 

10. Klineberg, 0., Asch, S. E., and Block, H. "An Experimental 
Study of Constitutional Types," Genet. Psychol. Hon., 1934, 
1 6, 140-221. 

11. Klineberg, 0., Fjeld, H. ? and Foley, J. P., Jr. "An Experi- 
mental Study of Personality Differences among Constitu- 
tional, * Racial, 3 and Cultural Groups." (To appear.) 

12. Kliiver, H. "An Analysis of Recent Work on the Problem 
of Psychological Types," /. Nerv. and Mental Diseases, 
1925, 62, 561-596. 

13- "The Problem of Type in "Cultural Science Psychol- 
ogy/ " / Phttos., 1925, 22, 225-234. 

14- "Studies on the Eidetic Type and on Eidetic Im- 
agery," Psychol. Bull, 1928, 25, 69-104. 


15. Kretschmer, E. Physique and Character (transl. from 2nd 
ed. by W. J. H. Sprott). N. Y.: Harcourt, Brace, 1925. 
Pp. 266. 

1 6. . Korperbau und Charakter (Tenth edition). Berlin: 

Springer, 1931. Pp. 240. 

17. McDougall, W. Outline of Abnormal Psychology. N. Y.: 
Scribner's, 1926. Pp. 572. 

1 8. Mohr, G. H., and Gundlach, R. H. "The Relation between 
Physique and Performance," /. Exper. PsychoL, 1927, 10, 

19. Naccarati, S. "The Morphologic Aspect of Intelligence," 
Arch. PsychoL, No. 45, 1921. Pp. 44, 

20. . "The Morphologic Basis of the Psychoneuroses," 

Amer. J. Psychiat., 1924, 3, 527-545. 

21. Naccarati, S., and Garrett, H. E. "The Relation of Mor- 
phology to Temperament," /. Abn. and Soc. PsychoL, 1924- 
*5, *9, 254-263. 

22. Pavlov, I. P. Conditioned Reflexes: an Investigation of the 
Physiological Activity of the Cerebral Cortex (transl. and ed. 
by G. V. Anrep). Oxford Univ. Press: Humphrey Milford, 
1927. Pp.430. 

23. Sheldon, W. H. "Morphologic Types and Mental Ability," 
/. Pers. Res., 1927, 5, 447-4S 1 - 

24. . "Social Traits and Morphologic Types," /. Pers. 

Res., 1927, 6, 47-55. 

25. Spranger, E. Types of Men (transl. by P. J. W. Pigors). 
Halle: Niemeyer, 1928. Pp. 402. 

26. Stockard, C. R. "Human Types and Growth Reactions," 
Amer. J. Anat., 1923, 31, 261-288. 

27. Weidenreich, F. Rasse und Korperbau. Berlin: Springer, 
1927. Pp. 187. 

28. Wertheimer, F. L, and Hesketh, F. E. "The Significance 
of the Physical Constitution in Mental Disease," Medicine, 
1926, 5 ^ 37S~463- 


f variations from trait to trait within the 
individual is of both practical importance and theoretical 
significance. When a child is classified as intellectually* 
inferior on the basis of, let us say, Stanford-Binet I.Q., 
there is still much that remains to be known about his 
mentality. Is he equally inferior in all respects or does he 
exhibit significant discrepancies in his mental develop- 
ment? Is he normal or even superior along some specific 
lines ? Similarly, in the case of a child of very high I.Q., 
we may inquire in what ways he is superior. How uni- 
formly does he excel the average child in intellectual per- 
formance? The intelligence test, furnishing a single sum- 
mary - figure to characterize the child's general mental 
level, often obscures important facts. Two individuals 
obtaining the same total score may present very different 
"mental pictures" when their performance along specific 
lines is analyzed. 

The skilled clinician or mental tester has always taken 
this into consideration in interpreting test scores. The 
child's performance on the different parts of an intelligence 
scale and even, when feasible, on several different kinds of 
tests, is carefully analyzed before a final judgment is 
offered. In this way, the practical common sense of the 
examiner is brought in to remedy a deficiency in the test 
itself. There is a rapidly growing realization, however, 
that the question of variation among the individual's 
abilities deserves serious and systematic consideration and 
should be investigated in its own right. This problem is 



gradually coming to be regarded as even more important 
than the establishment of the individual's general level of 

In planning an educational program for a given in- 
dividual, or in helping him to choose a vocation, it is of 
the greatest importance to know his strong and his weak 
points. Total scores on intelligence tests can be used only 
in v a very crude""affd general sort of educational and vo- 
cational guidance. In the comparative study of groups, 
such as the sexes or different racial or cultural groups, a 
consideration of the general level of ability may also prove 
misleading. Let^u&.^uppose,. . for example, -that- one^such 
group excels markedly in ability A and the other m abjlity 
Bs.... If both are examined, with an intelligence test jvhich 
55J5P-! e ? Cities A and, B,, equal extent, no difference 
* n Jfi ta l s c oi *e will appear jDetweea r thje ,twp groups. Essen- 
tial and large differences might thus be concealed by the 
practice of lumping a number of tasks indiscriminately in 
the effort to arrive at the general mental average called 

Much confusion has likewise been introduced into the 
interpretation of test results by the common tendency to 
take labels too seriously. Thus, if two tests are labeled 
measures of " intelligence," it is assumed that they are 
measuring the same characteristic of the individual. It is 
therefore most disconcerting to discover that the same 
child may appear dull in one intelligence test and above 
average in another. Such cases are, however, found. 
Since intelligence scales consist of a more or less random 
sampling of different tasks, the specific abilities covered 
by the various tests may differ. Some tests, for example, 
may be more heavily "loaded" with verbal items, others 
with mechanical items. -Even successive levels of the same 
test occasionally involve different abilities. Thus the 


Stanford-Binet draws more heavily from the verbal field 
at the higher year levels than it does at the lower. The 
same child tested with the Stanford-Binet at different 
ages might be favored at one time and handicapped at 
another because of the particular abilities called into play. 
If the individual's abilities were all more or less on a 
dead level, a single summary score would be quite informa- 
tive. But if appreciable variation in the individual's 
standing in different traits is the rule, then such a score 
is crude at best and may upon occasion be definitely mis- 
leading. It is essential, therefore, to inquire into the extent 
of variation within the individual. The data on this 
question have been gathered from a variety of sources. 
Case studies are available of individuals who exhibit 
marked asymmetry of development along different lines. 
Such individuals can be found among the feebleminded 
and the intellectually superior, as well as among the nor- 
mal. Quantitative measurements have also been made on 
the extent of variability from trait to trait in large random 
samplings. Finally, correlational analysis throws some 
light upon this problem. Typical data obtained by these 
various approaches will be examined. 


Among the feebleminded, persons are occasionally met 
who display an exceptional talent along some specific line. 
Such individuals have been designated "idiots savants" 
(wise idiots). This term has been criticized for being 
somewhat misleading. The usual idiot savant is neither 
particularly wise nor an idiot. He is not sufficiently defi- 
cient to be classified as an idiot, but is frequently found at 
the moron or borderline level. And he is "wise" only in a 
very limited field. In the practical management of his 
own life he is ordinarily a complete failure. Many of the 


idiots savants in institutions for the feebleminded were 
physically awkward or uncouth, had a serious sensory 
deficiency, or were reputed to be emotionally unstable or 
irresponsible. Otherwise they might have been able to 
shift for themselves with a little assistance, by capitalizing 
their special talent. As is true of all extreme deviations in 
the distribution of any trait, idiots savants are relatively 
rare. Because of their striking quality, however, such 
cases attract a good deal of attention, so that a number of 
fairly complete descriptive accounts are now available. 

ThejpeciaHalent of the idiot savant maj^ be observed in 
j>a<^^ activity. Mechanical 

aptitude, ability in drawing and painting, a phenomenal 
memory, arithmetic proficiency, a special gift in music, all 
are represented. Thjonj5eld from which idiots savants 
s fSL?*L k?, conspicuously . , absentJs , that' Q| linguistic or 
verbal aptitude. 1 This fact throws some light upon our 
concept ol "general intelligence. As will be more fully 
demonstrated in the following chapter, the latter is very 
largely identified with verbal ability. Most intelligence 
tests are composed, to a very great extent, of verbal tasks. 
Success in the practical business of everyday life is also 
more closely linked to linguistic facility than to other 
traits. A serious deficiency in the power of verbal expres- 
sion will thus brand an individual as incompetent from 
many points of view. Conversely, a person who is es- 
pecially proficient in verbal traits may thereby compensate 
for deficiencies along other lines and will rarely, if ever, 
find his way into an institution for the feebleminded. No 

1 Feebleminded individuals have been described who could repeat long quota- 
tions in several foreign languages, without error and with perfect accent. But 
these cases probably represent a more specific abnormal phenomenon and can- 
not be regarded as having superior linguistic endowment in the usual sense. 
Such individuals, for example, are frequently unable to read or write. (Cf. 
Barr, 4, for a report of such a case.) 


other single talent seems to be such a saving grace in our 

Several cases of special talent in pictorial art have been 
found among the feebleminded. Such individuals are able 
to execute excellent reproductions of well known paintings. 
Occasionally this talent passes beyond mere copying and 
suggests real creative genius. Such a case is that of Gott- 
fried Mind (35, p. 336) 3 diagnosed as a cretin imbecile. 
His mental deficiency was manifested from an early age. 
He was unable to learn to read and write. His movements 
were awkward, his hands large and rough, and his general 
appearance that of the traditional mental defective. Since 
he showed considerable talent for drawing, he was given 
some instruction in this field. His subsequent success in 
pictorial art was phenomenal. Because of his excellent 
drawings of cats, he came to be known as a The Cats' 
Raphael" In addition, he produced drawings and water- 
color sketches of deer, rabbits, bears, and groups of chil- 
dren, which were remarkable for their life-like quality and 
masterly execution. His fame spread throughout Europe 
and one of his pictures of a cat and kittens was purchased 
by King George IV of England. 

An equally remarkable case is that of J. H. Pullen, who 
has been called "The Genius of Earlswood Asylum" (35, 
pp. 340-345). This individual had extraordinary mechan- 
ical ingenuity coupled with talent in drawing and carving. 
In other respects he was very deficient. He did not talk 
until the age of seven, and for a long time only uttered 
the word "muvver." His speech was always imperfect, 
and he is reported as being very deaf. He was taught by 
his family to write and to spell the names of simple objects, 
and this constituted the extent of his schooling. From an- 
early age, he spent much of his time in drawing or in carv- 
ing ships out of pieces of firewood, occupations in which he 


showed considerable proficiency. At the age of 15, he was 
admitted to Earlswood Asylum, where he was put to work 
in the carpenter's shop and soon became an expert crafts- 
man. During his sixty-six years at the asylum, he pro- 
duced an impressive array of beautiful and highly in- 
genious objects, including crayon drawings, carvings in 
ivory and wood, excellent models of ships, and various 
mechanical devices. Occasionally he even designed his 
own instruments to help him in his work. 

One of Pullen's constructions was a representation of 
a gigantic human form, thirteen feet high. This full- 
fashioned "robot" could be made to execute a variety 
of movements such as raising the arms, rotating the head, 
protruding the tongue, opening and shutting mouth or 
eyes, etc. Another remarkable construction was a model 
of a ship, beautifully executed in the minutest detail. 
This model required over three years for its completion 
and attracted universal admiration when exhibited. Pul- 
len's work revealed artistic imagination as well as mechan- 
ical ingenuity, skill in planning, and painstaking execution. 
Being cut off from many ordinary sources of stimulation 
by deafness, it is probable that he concentrated all his 
efforts from childhood upon the development of this one 
remarkable talent. In regard to general personality de- 
velopment, he is described as childish and immature, emo- 
tionally unstable, and lacking in common sense. 

Special talent in music has also been repeatedly ob- 
served among the feebleminded. A very striking case 
(35> P- 339) of exceptional musical ability combined with 
serious defect in other respects is that of a woman in the 
Saltpetriere, a famous French institution for the feeble- 
minded and the insane. This patient was an imbecile, 
blind from birth, a cripple, and affected with rickets. 
She was, however, able to sing without error any selection 


which she had heard. It became customary for her fellow- 
inmates to come to her so that she might correct their 
mistakes in singing. She attracted wide attention, and one 
day the composers Liszt and Meyerbeer visited her " sing- 
ing class " to bring their encouragement and consolation. 

Recently, a similar example of musical talent has been 
investigated by the use of standardized intelligence tests 
(cf. 26). This was the case of a boy admitted to a feeble- 
minded institution at the age of 14. He came from an 
intellectually superior family which included many musi- 
cally gifted individuals among its members. As a child, 
the subject was intellectually normal and manifested his 
musical talent from an early age. When three years old, 
he had pneumonia and meningitis, and since then he under- 
went steady mental deterioration. Upon admission, his 
I.Q. was 62; at the last testing, it had dropped to 46. 
He was then over 20 years of age and had a mental age of 
7 years-5 months. His memory was unimpaired, how- 
ever, and he retained his excellent musical ability. Al- 
though never known to compose a piece, he could play 
difficult music by ear and was also able to read difficult 
musical compositions at sight. 

The feats of memory performed by some feebleminded 
individuals have often attracted notice. Tredgold (35, 
p. 337)3 for example, describes a 65-year-old mental de- 
fective in Earlswood Asylum with a remarkable memory 
for historical facts. He could repeat the dates of birth 
and death and the essential facts of the life of any prom- 
inent character in history. This knowledge was acquired 
largely by rote, through poring over all available books on 
biography and history. It was not, however, a matter of 
sheer meaningless repetition, as was shown by the subject's 
responses when questioned on the material. Another pa- 
tient at the same institution showed an excellent memory 


for dates and occurrences which had come within his own 
experience. He proved a useful source of reference on local 
happenings in the institution. 

Arithmetical prodigies have also been found among the 
ranks of the feebleminded. Usually, the skill manifested 
is confined to the mechanics of computation. Thus the 
subject may perform long and complicated calculations 
within a very short time and without the aid of paper and 
pencil. A favorite feat is to determine the number of min- 
utes a person has lived, from a knowledge of his age or 
date of birth. Multiplication of three-place numbers, nam- 
ing square roots and cube roots of four-place numbers, and 
similar difficult operations have also been executed within 
a few seconds. In some cases, this numerical aptitude goes 
beyond routine computation, as is indicated by the in- 
dividual's ability to solve mathematical problems ex- 
pressed in fairly elaborate and confusing terms. 


Asymmetry of mental development is not to be regarded 
as characteristic of the feebleminded. It is equally com- 
mon outside of institutions and among those classified as 
normal or superior on the basis of intelligence test per- 
formance. As was found in the case of the feebleminded, 
verbal traits are closely linked with what is termed " gen- 
eral intelligence" and therefore offer no examples of special 
talent. Children who are deficient in reading or spelling 
are usually inferior on intelligence tests. 1 Occasionally, a 
young, bright child is a poor speller because of his distaste 
for the routine drill necessary to master this school sub- 
ject, but the inferiority is usually overcome. Juvenile 
authors, furthermore, have invariably been children of 
very high LQ. 2 In many other traits, however, marked 

1 Cf. L. S. Hollingworth. (16, Ch. IV and V). 2 Cf. 17, Ch. IX, for examples. 


discrepancies have been found between the child's alleged 
"general mental level" and his ability along specific lines. 
Musical aptitude seems to have little or no relationship 
to ST^eno^ntelligence. This was clearly shown in a study 
by*L. S. Holiingworth (18) qn^g intellectually gifted 
cjiildren. All of the subjects were"' enrolled in special 
classes conducted for children with LQ.'s of 135 or higher. 
The median Stanford-Binet I.Q. of this group was 153 
and the range extended from 135 to 190. la chronological 
age,jthe children corresponded, closely to the t ,group of fifth 
gradeschoolchildren upon whom the Seashore tests of 
musical sensitivity l had been standardized. Accordingly, 
the scores of the intellectually superior children on these 
tests were expressed as percentiles of Seashore's fifth grade 
group. The average percentile scores thus obtained on 
each test are given below. 

Test Average Percentile Score 

Pitch 47 

Intensity 50 

Time 58 

Consonance 48 

Tonal memory 52 

A percentile score of 50, it will be recalled, corresponds to 
the middlemost score of the standardization group and 
thus represents a "normal/' or average, performance. 
The closeness to 50 of all the average percentile scores of 
the superior group indicates that musical aptitude is dis- 
tributed among these children in very much the same 
fashion as in any group of the same age, chosen at random. 
Although in intelligence test performance these subjects 
were all within the upper i% of the general population, 

1 For a description of these tests, cf. Seashore, C. E. The Psychology of Musi- 
cal Talent. N.Y.: Silver, Burdett, 1919. Pp.288. 


their individual percentile scores on the music tests ranged 
from zero to 98. 

Case studies of arithmetical prodigies and " lightning 
calculators'' suggest that numerical aptitude is likewise 
distributed independently of general intelligence. Many 
such cases, from the early Greeks to the end of the last 
century, have been brought together by Scripture (31) 
and later by Mitchell (27). In r^ai^to^lieir % ;achievements 
along other lines^or their practical ability to sucqeecfin 
every^ay^Hfe^mathematicaLpiociigies rua the gamut, from 
genius and eminence of the highest order to mental, dull- 
ness." A few would no doubt be classified as "borderline" 
or lower on current intelligence tests. At the other ex- 
treme are such men as Gauss and Ampere, whose excep- 
tional talents covered a wide range, and who have made 
distinguished contributions in mathematics and allied 
fields. These men were " lightning calculators," but also 
possessed very superior ability along many other lines. 
For the present purpose, however, we are concerned with 
cases of asymmetrical development in which prodigious 
arithmetic powers are coupled with mediocrity or defi- 
ciency in other respects. 

Henri Mondeaux (cf. 31), the untutored son of a poor 
woodcutter, is a famous example of remarkable arithmetic 
ability in an otherwise dull person. In his childhood he 
received no instruction, but was sent to tend sheep at the 
age of 12. While engaged in this occupation, he amused 
himself by counting and arranging pebbles; by this means 
he learned to carry out arithmetic operations. He worked 
out for his own use many special devices and aids to com- 
putation. After long exercises at these calculations, he 
offered to tell people he met the number of seconds in 
their ages. At this time, a schoolmaster became interested 
in him and offered to instruct him. Unfortunately the 


boy had a very poor memory for names and addresses 
and he spent nearly a month searching the city before he 
was able to locate his benefactor. Mondeaux was subse- 
quently exhibited by his teacher at several colleges and 
universities and in 1840 he was presented before the 
Academy of Sciences at Paris. His was not merely a talent 
for routine calculation. He demonstrated his ability to 
solve, by ingenious devices of his own making, complex 
problems such as the following: 

There is a fountain containing an unknown quantity of 
water; around it stand people with vessels capable of con- 
taining a certain unknown quantity. They draw at the fol- 
lowing rate: the first takes loo quarts and -fa of the remainder; 
the second takes 200 quarts and T V f the remainder; the 
third 300 quarts and T V f 'the remainder, and so on until 
the fountain is emptied. 

Mondeaux gave the correct answer to this problem in a 
few seconds and then explained the method whereby he 
had arrived at the solution. 

A similar case is that of Tom Fuller, a Negro slave 
brought from Africa at the age of 14. He could neither 
read nor write and received no formal instruction. As in 
the case of Mondeaux, his arithmetic was entirely self- 
taught. It is reported of him that when asked how many 
seconds a man had lived who is 70 years-iy days-12 
hours old, he gave the answer, after ij minutes, as 
2,210,500,800 seconds. One of his questioners had mean- 
time been computing with paper and pencil and informed 
Fuller that he had arrived at a different number, which he 
read off. At this, the Negro immediately pointed out that 
his questioner had forgotten to allow for leap years ! 

A few cases of " lightning calculators " have been directly 
observed and investigated by psychologists. 1 

1 Cf. Binet (6) and Lindley and Bryan (23) . 


tiQnjjxus.uQbtained, as well a.s_ the. careful analysis- of avail- 
ably reports on arithmetic prodigies, has brought to light 
certain characteristics of these individuals which may 
account for their talent. Injmost cases, the individual has 
worked out a number of short-cuts and special devices 
which ..enable him to compute far more efficiently than is 
ordinarily possible. Secondly, such .individuals have usu- 
ally .memorized many more number combinations, such as 
squares, cubes, roots, products, etc., than are at the dis- 
posal of the average man. Arithmetical prodigies in- 
variably manifest a very keen interest and fascination 
for numbers; as a result, they devote much time to analysis 
of computation methods and drill which would otherwise 
prove very monotonous. Mairy^also seem to have a large 
perception 3pan, which enables them to grasp a long series 
of-mimbers simultaneously, as well as vivid imagery, mak- 
ing_pQ3sihle " mental computation" without the aid ? of 
paper and pencil. 

The examples which have been reported suffice to illus- 
trate the existence of extreme asymmetries of mental de- 
velopment. It is apparent that talent along certain lines 
is not incompatible with mediocre or inferior status in 
others. The cases so far described represent extreme devi- 
ations which for that reason are easily recognizable. Other 
instances of special talents or deficiencies, not so striking 
as to attract widespread attention, but revealed by the 
application of quantitative techniques of measurement, 
will be found in the following section. 


In the effort to obtain a more objective and concrete 
picture of variations within the individual than is furnished 
by the general impression of the examiner, a psychograph, 
or profile chart* of the individual may be drawn up. The 


psychograph shows at a glance the relative standing of the 
subject on any number of tests or other measures. The 
individual's scores on all tests must first be transmuted 
into comparable units. This is the fundamental step in any 
attempt to study variations within the individual. The 
psychograph itself, in the sense of a pictorial representa- 
tion, could easily be dispensed with. The same informa- 
tion,, although in a less vivid form, could be got from an 
examination of a set of scores obtained by the individual, 
provided that all scores are expressed in the same terms. It 
is in this latter respect that the judgment of the examiner 
needs to be supplemented by quantitative techniques. 
Confronted with a set of scores, some of which are ex- 
pressed in seconds, others as number of words recalled, and 
still others as number of problems correctly solved, the 
clinician would be at a complete loss. 

Comparable measures can be obtained in several ways. 
If all the tests have been standardized in terms of age, 
each score can be expressed as a ^en^l^ge. 1 In many 
situations, however, this is not feasible. Some tests, es- 
pecially in the field of personality, do not exhibit large or 
systematic age changes. The range of variation within 
one age group might thus be greater than the largest dif- 
ference between the average performance of age groups. 
The application of the mental age concept to adult sub- 
jects, furthermore, is a rather questionable practice. 

A commonly employed and generally applicable meas- 
ure is the^^n^^ score (cf. Ch. II). A percentile, it will 
be recalled, gives tET^percentage of individuals whose 
scores fall at or below that obtained by the given subject. 
Percentiles are determined once and for all in the process 

1 A mental age psychograph is employed at the N. Y. C Children's Hospital, 
an institution for the feebleminded. (Cf. Poull, L. E. " The Psychographic 
Method in Clinical Practice." /. Appl. PsychoL, 1936, 20, 161-164.) 


of standardization. The test is administered to a large 
group, representative of the population upon which it 
will ultimately be employed, and the percentage of in- 
dividuals who score at or below each point is determined. 
Thus, if on an arithmetic reasoning test, 10% of the sub- 
jects correctly solve three problems or less, then any child 
who completes three problems correctly receives a per- 
centile score of 10. A percentile scale divides the group 
into 100 classes, each composed of the same number of 
persons. Any subject subsequently taking the test is then 
placed into one of these classes, the poorest corresponding 
to the first percentile and the best to the looth percentile. 
A subject who receives a percentile rating of 100 has ob- 
tained the highest score reached in the standardization 
group, but not necessarily the maximum score possible on 
the test. Similarly, a zero percentile rating does not mean 
a zero score; it signifies only that the subject's score is 
lower than that obtained by any member of the standard- 
ization group. 

Scores from different tests can also be made comparable 
by the use of standard measures. 1 In this case, the subject's 
score is exp res s edT^FT'Heviation above or below the aver- 
age of a given group. Thus if his original score falls exactly 
at the average, he receives a standard score of zero. If he 
is better than average, he receives a plus score, if poorer 
than average, a minus score. The unit in terms of which 
the scores are reported is the standard deviation (S.D.) of 
the distribution. Thus, if the average of the distribution is 
35 and the S.D. 10, and if a given subject obtains a* score of 
45 points, his standard score would be +I 3 or one standard 

/ A r> o r \ 

deviation above the group average ( = i ). Simi- 
larly, if another subject receives a score of 30 on the same 
1 Cf. Kelley (21), pp. 114-117. 


(3 ~~ 35 A 

= .5!- 

If the distribution of scores on the different tests can be 
assumed to be of the same general shape, approximating 
the normal bell-shaped curve, the standard scores com- 
puted from them will be directly comparable. 1 

It should be borne in mind that none of these techniques 
for converting scores into comparable measures yields a 
scale of equal units. They simply express, in terms which 
are more or less int^lVi^^^^^ relative position oi the in- 
dividual in different tests, but they do not furnish a precise 
statement of the actual amount of trait difference repre- 
sented by the various scores. Thus, it will be recalled that 
the mental age unit corresponds to the average change in 
score occurring during a one-year period. Successive men- 
tal ages will not, therefore, represent equal increments of 
ability. We know that an M.A. of 6 indicates a higher 
standing than an M.A. of 5, and that an M.A. of 10 in- 
dicates a higher standing than one of 9, but we cannot 
conclude that the amount of difference is the same in both 

Nor can percentile scores be interpreted as equal ability 
units. As was shown in Chapter II, such an interpretation 
would imply that the distribution of the trait measured is 
rectangular. Since, however, traits are distributed accord- 
ing to the normal bell-shaped curve, individuals will 
cluster more closely at the center of the distribution and 
scatter as the extremes are approached. As a result, a 
difference of one percentile point at the extremes corre- 

1 Hull (19) has described a technique for obtaining comparable measures by 
transmuting the original scores into a distribution with any desired average and 
S.D. This procedure is based upon the same principle as standard measures. 
Its chief advantages lie in the fact that the scores can be expressed in more 
familiar terms than by the use of standard measures, and that negative values, 
decimals, etc., can be eliminated. 


spends to a much greater difference in amount of the trait 
than does a difference of one percentile point nearer the 
center. The difference between an individual who re- 
ceives a percentile rating of 90 in height and one who re- 
ceives a percentile rating of 91 is much greater, in actual 
inches^ than the difference between two individuals re- 
ceiving percentile ratings of 50 and 51. 

Similarljr^taiidard.acore,a,dD not represent equal units. 
BjLSuhte&cting a constant (the average) and dividing by a 
cQastan.._(the $.D.)> we^o^jiot, Baiter T ,the scares in, any 
The set of measures is simply transmuted 

into a different system of expression, as when pounds are 
changed to kilograms. Rirtthe.staadard scores so .obtained 

which were present 

^liSSS^-SSS 8 }??;??* X 
In addition to the different ways of expressing com- 

parable scores, there are a variety of ways in which the 
psychograph itself can be plotted. Illustrations of differ- 
ent kinds of psychographs will be found in Figures 39-45. 
Figure 39 shows a horizontal bar diagram. It will be noted 
that no scores are available for the subject on a number of 
tests listed in the psychograph. The use of horizontal bars 
which are not joined is necessary in such a case, since a 
continuous line would be inapplicable. The boy whose 
abilities are pictured in this psychograph exhibits a fairly 
clear-cut tendency to excel in motor performance. His 
score becomes progressively poorer as we pass from the 
strictly motor, through sensori-motor and perceptual, to 
more highly "intellectual" or verbal functions. His "men- 

1 Equal units can, of course, be obtained by the use of scaling techniques. 
This, however, is a laborious procedure, requiring the testing of a large, repre- 
sentative, and normally distributed sampling of individuals. The question of 
equal units is no more essential, furthermore, for the measurement of trait 
variability than for any other problem involving mental tests. It has been 
brought up in this connection solely because of a rather common tendency 
erroneously to treat transmuted measures as equal unit scales. 




MENTAL AGES. (After H. L. Hollingworth, 15, p. 208.) 

tal age" on the different tests ranges from ir years in a 
test of following written directions to slightly over 18 in 
hand grip. 

Figure 40 illustrates the use of a circular psychograph, 
plotted in terms of percentile scores. The center of the 
circle corresponds to a zero percentile, the outermost cir- 
cumference to 100 percentile., and the middlemost cor- 
responds to an average performance. The radii indicate 
the individual's relative standing in different functions. 
This psychograph shows a boy, slightly above average 
in intelligence, who is fairly uniform in most of the traits 
measured. With one exception, his percentile ratings vary 
between 45 and 70. In mechanical aptitude, this boy seems 
to have a special talent, obtaining a percentile score of 
95 on the Stenquist Mechanical Aptitude Test. 

Figures 41-45, inclusive, illustrate the continuous line 
psychograph. In Figure 41 will be found the psychograph 





1. Stanford -Binet 

2. Trabue Completion Test 

3. Cancellation 

4. Digit-Symbol 

5. Opposites 

6. Stenquist Mechanical Ability Test 

7. Tonal Memory 

8. Pitch 

9. Time 

10. Intensity 

11. Healy Pictorial Completion 

12. Grip in Hand 

TERMS OF PERCENTILES, (After L. S. Hollingworth, 16, p. 41.) 



Handwriting, School Marks__. 

Drawing, School Marks 

Drawing Cart 

Drawing Horse 


Cancellation Triangles 

Perceptual Learning 

Lincoln and Pig, Deferred 

Lincoln and Pig, Immediate __ 

Marble Statue P 

Aesthetic Appreciation 

Code 1-g 

Punched Holes 

Spatial Relations 

Thurstone Hand 

Thurstone Reasoning 

Bonser Reasoning 

Proverbs . 

Trabue Completion . 

Word Building- _ 

School Standing. 

BinetLQ . . 





of a girl who falls within the lowest 10% in LQ. and in 
school standing, and is below average in most verbal tests 
of intellectual functions. But she exhibits exceptional 
talent in representative drawing. When tested, this girl 
was in the sixth grade at the age of 14. Many members of 
her family were reported as interested and talented in 
drawing or painting. Figure 42 shows the psychograph of 


01Q|20[ 3p[ 40[ 50 





Tonal Memory 

Drawing (Ratings) 

Grip in Hand 



General Intelligence*. 
(Stanford-Binet; Alpha) 



40 50 

70 80 


60 71 


90 100 

P- I7S-) 

a 14-year-old girl of average general intelligence, with 
exceptionally high ratings in music and drawing. This 
subject was referred for psychological examination because 
she was doing poorly in school. She had been attending a 
superior private school in which the average LQ. was 120, 

2 7 8 


a fact which accounts for her apparent backwardness. In 
this school, she had been receiving good grades only in 
music and drawing. In Figure 43 is given the psychograph 


010J 20 30 40[ 50 

60| 70J 80| 90J100 

f Pitch - - 












Tonal Memory 



Drawing (Ratings) 


Grip in Hand 




General Intelligence- 
(Stanford-Binet; Alpha) 


010| 20 30 40 50 

60J 70| 80 j 90J100 

16, p. 179.) 

of a I o-y ear-old schoolboy. On intelligence tests this boy 
ranked close to the looth percentile, having an I.Q. of 151. 
In reading, arithmetic, and elementary science, his school 
work was excellent. In music tests, on the other hand, he 
ranked consistently low; his music teacher regarded him 
as a complete failure and advocated that he repeat the 

Figures 44 and 45 have been plotted in terms of standard 
scores. Both are taken from a series of psychographs con- 




Age norm for 6 years 







* B 


SCHOOLGIRL. (After DeVoss, 8, p. 350.) 

structed by DeVoss (8) on children who had been selected 
for their high intellectual level. 1 The psychograph in 
Figure 44 is that of a girl with a Stanford-Binet LQ. of 192. 
This child, although above her age norm in all of the tests 
but one, exhibits marked discrepancies among her scores. 
She is highest in arithmetic reasoning and also shows un- 
usual ability in tests involving reading comprehension. 
In four information tests dealing with science, language 
and literature, history and civics, and music and art, she 
obtained much lower scores. In the last named test, her 

1 Part of the group employed by Terman in his extensive investigation OP 
gifted children (cf. Ch. XIII). 



score was even slightly below her age norm. In Figure 45 
is the psychograph of a schoolboy with an LQ. of 155, who 
presents a very different mental picture. He is best in 

SCHOOLBOY. (After DeVoss, 8, p. 360.) 

music-art information, second best in history-civics in- 
formation, and poorest in arithmetic reasoning and com- 
putation. These examples illustrate the fact that intellec- 
tually superior children, although above their age norms in 
most mental tests, may be much farther above average in 
some traits than in others. 


The term A^tW by Hull 

(20) to designate variability from ' 


individual. This is to be distinguished from individual 
^^^^^.^hickjefers to the differences among individuals 
in a single trait. All of the statistical techniques commonly 
enapToyed to measure the amount of individual variability 
can be applied to the measurement of trait variability, 
provided that the scores on different tests are expressed in 
the same units. 

In a study by Hull (20), an attempt was made to meas- 
ure the amount of variability in different traits and com- 
pare it with the amount of individual variability on single 
tests. The scores of 107 high school freshmen on 35 tests 
were obtained. 1 The tests included several subtests from 
intelligence scales, as well as tests of motor characteristics, 
perception, attention, and personality traits. Each of 
the 35 sets of scores was transmuted into a distribution 
with an average of 81 and an S.D. of 7 by a method similar 
in principle to that employed in obtaining standard scores 
(cf. Hull, 19). The particular values chosen for average 
and S.D. are arbitrary and were selected chiefly because 
of their similarity to school grades. 

With these converted scores, the S.D. of each individ- 
ual's scores in the 35 tests ivas computed as a measure of 
thelimount of trait variability. There were thus obtained 
as many S.D's as there were subjects, viz., 107. T^^a^Gr- 

P' P^..T$wfo> '4$ A$, units 
employed, represents the individual variability.^ .any QJie 

^"UMMiMiiwllMttiJWMfci^ ,,-,,;,.''-.*<,- ' i w ' r 

of^he t^sts. After allowing for possible chance errors of 
sampling and measurement, 

The.. exact relationship obtained between these two forms 
of variability is, however, affected by the homogeneity of 

1 The original data were collected by C. E. Limp in connection with an in- 
vestigation of shorthand and typewriting aptitudes. 


the group employed. The more homogeneous the group, 
the smaller will be the original S.D.'s representing in- 
dividual variability in raw scores. Because of the trans- 
mutation technique employed, this will automatically 
make the deviations within the individual appear larger. 
The group of high school freshmen upon whom Hull's 
data were obtained was a fairly representative sampling, 
covering a wide range. His results are therefore typical of 
what would be found on many groups. A universal esti- 
mate of the amount of trait variability can never be 
arrived at, however, because such a measure depends in a 
peculiarly intimate fashion upon the nature of the group 
within which it is obtained. 

ttl? nevertheless apparent from this study that a large 
amount of trait variability may be found withia a group 
of normal individuals who were not selected on the bans of 
asymmetrical development. The amount of trait variability 
also differed with the individual. Some subjects displayed 
much more uniformity than others in their performance on 
different tests. The individual S.D.'s of trait variability 
ranged from 4.3 to 9.09. The distribution of scores of each 
individual on the 35 tests seemed to follow the general 
form of the normal curve. MasJLof Jthe individual's scores 
cj^stered about his own average, only a few scores deviat- 
ing markedly from it in either direction. Fi#alit]2*.fl& re- 
of ability and the extent of T his^tr|Lit^ variability. There 

i n ~ 
dividual witt^^^ 

ual's average score on all the tests f and Jii^trait^variability 

* ulM- ^ kl *- % * 4 ''*'*' TJ "*"""' 

coiiducted^ determine 

whether gift^c^ldlW,,,M^,MlJ^B OTQ specialized in their 

"^^^^^^^-^ p * u ***.*^^^ 


intellect^l fc abniitie5,tb.ai3...nGPmal children. A group of 
100 subjects were selected on the basis of mental" age Jfrom 
a larger "group of "gifted children" employed by Terman 
(cf. Ch. XIII). The mental ages of DeVoss' group ranged 
between 14 and 15-5, with an average of 14-8; the chrono- 
logical ages ranged from 8-6 to n-i. The average LQ. 
was 149.4, and the range from 136 to 1 80. In school grade, 
the children were scattered from the third to the eighth 
grade, inclusive. Tb^se^^ ,with -r a 

^of^ unselected eighth grade schoolchildren 

ages as, the, superior 
group. Both groups were given the Stanford Achievement 
Test, consisting of seven subtests on different school sub- 
jects, as well as information tests in special fields. All 
scores were reduced to standard measures. 

within each sub- 
.differences .large enough to 

By means of a specially devised statistical 
formula, 1 it was possible to estimate how large a trait 
difference might be obtained simply through the opera- 
tion of chance factors, such as inadequacies in the tests 
employed. Upon the application of this formula, it was 
discovered that a large percentage of. the trait . 
felTbe^nd the chanq^Jiiaits, and.mpst t 
a triiejiisxxrepancy in the individual's staading,in4he traits 
compared. In Table XIII are given the percentage of trait 
differences, in both the gifted and control groups, which 
fell outside of the distribution of differences expected by 
chance. The percentages in the gifted group are given 
above the diagonal, those in the control group below the 
diagonal The tests which are being compared are in- 
dicated in the top row and first column to the left. Thus, 

1 A formula for the computation of the P.E. of the difference between an 
individual's standard scores on any two tests. 



in the gifted group, 24% of the differences between scores 
on arithmetic reasoning and computation fell beyond the 
chance limits ; the corresponding percentage for the control 
group is 34%, and so on. 





(After DeVoss, 8, p. 325) 

Tests to Be 


.& ^ 

1 *s 
1 5 





tf ? 


s v> 

txo txo 



*- o 





































V 3 
























v 33 


























\ k 









* Gifted group above the diagonal: upper right-hand block. Control group 
below the diagonal: lower left-hand block. 

It will be noted that in every test pair compared there 
are found differences over and above those expected by 
chance. This is true of both gifted and control groups. 
The percentages of such differences are also closely similar 
in the two groups, test by test. In the gifted group, the 


percentages vary from 13 to 37, in the control group from 
13 to 40. The average percentages are 28.89 an< 3 27.82 
for gifted and control groups, respectively. Out of the 
28 inter-test comparisons given in Table XIII, the gifted 
group has the larger percentage of excess differences 13 
times, the control group has the larger percentage 12 
times, and the two have identical percentages in 3 cases. 
Thus t there .seems to be no appreciable or consistent dif- 
ference in, trait variability between intellectually normal 
and superior children. 


The examination of extreme examples of asymmetrical 
t, _ as, well as the measurement, of .trait variabil- 
in general, suggests that. superior 
may be associated with inferior abilities 

injDther respects. It is not to be concluded from this, 
^SSZSIiJliS^ ^P m P ensa ^ on is. the rule. Superior standing 
in one trait does not imply inferiority in another. We have 
cited only examples in which individuals with a high 
standing in a certain trait A make a poor showing in a 
second trait B. We could with equal facility find cases in 
which the individual is superior in A as well as J?, or supe- 
rior in A and average in B. TJbis^juxi act 3 is wjiat ,w,^n 
by^jL???? SSn^i^ on - If *7 ar ious a ^llti&s jM:e..spedfi<sa.nd 
mutually independent, so that an i^dividuallso&taadii^ in 

,,>,. , Mvu ^^^^ml^m^m^^a^''^ , TOl - V <v*"rP"t^*^*. -!*""""' ""' -"' ' 

onejtells usjaothing about his relative standing,m aaajher, 
we should expect the correlation between such jtbiljties to 
be zero* "or" very low." Correraflon^tRus offers another ap- 
proac"h"to the analysis of trait variability. We may now 
turn to a consideration of some typical correlational results 
on the various traits suggested by case studies and psy- 
chographic analysis. 


findings with the Hevner tests of music appreciation are 
illuminating. In a group of 74 college students, Hevner 
(13) obtained a correlation of -.17 between one form of 
her music appreciation test and the Minnesota College 
Ability Test. The latter is very similar in its content to 
current intelligence examinations adapted to the college 
level. In the music appreciation test, four versions of 
parts of 24 musical compositions are rendered on the piano. 
These versions include the original and four distortions. 
One is a simplification of the music in which many of the 
tones are omitted, so that the music sounds bare, hollow, 
and uninteresting. In a second version, the music is 
elaborated by introducing additional tones into the chords 
and by ornamentation, so that the piece is overdone, con- 
fusing, and "frilly." In a third version, the melodic pro- 
gression or phrasing is altered, the music being thereby 
rendered formless and unbalanced. The subject is re- 
quired to state, in each case, which of the four versions he 
prefers. This test has been found to be quite diagnostic of 
musical aptitude, correlating highly with other music tests 
and independent criteria. 

The same subjects were given another form of the music 
appreciation test which included 48 items presented in 
only two versions, the original and one distortion. The 
correlation between intelligence test performance and 
scores on this test proved to be .15. The low negative 
correlations of these tests with intelligence would suggest 
a slight tendency for the more "intelligent" subjects to be 
inferior in music appreciation. The correlations are too 
low, however, to indicate a significant trend and the two 
traits can be regarded as practically unrelated. 

Intelligence has also been found to have little or no 
relationship with performance on the Seashore tests of 
musical sensitivity. In an investigation (9) on 230 college 


students, LQ.'s were estimated from scores on the Otis 
Self-Administering and Army Alpha. These I.Q.'s were 
correlated with scores on each of the Seashore tests, with 
the following results: 

Musical Test Correlation with LQ. 

Pitch .32 

Intensity .01 

Time .13 

Consonance .09 

Tonal memory .10 

Rhythm .12 

Aptitude in pictorial art shows a similar independence 

'^L^^^^ ^^^^jwaww mi*M&*~M*HH,uMi>***f''>ti*f t*-*i"< ' " ~" '" " '" " " ""'""' '"*>"""' " " < <J/--"- . . iw., 1 , ,,, 

of general jntdligence., Meier (25) obtained a correlation 
oCz^ytfi Jpetween the Terman Group Test of Intelligence 
and an art judgment test, within a group of 55 high school 
sSHentsl' Tfie same test correlated .018 with Thorndike 
Intelligence Test among 53 college students. Both correla- 
tions are sufficiently low to indicate an absence of relation- 
ship between the two traits. The art judgment test con- 
sisted of a series of pairs (or larger groups) of pictures 
reproduced in black and white. Within each pair (or 
group), one picture was the original, the other (or others) 
a variation which disrupted the organization of the picture 
by altering its symmetry, balance, harmony and unity, 
rhythm, or similar features. The subject was to indicate 
which picture he preferred in each case. 

In the effort to discover the relationship between draw- 
ing ability and other traits, Ayer (3) conducted an in- 
vestigation on 51 high school students. The subjects were 
shown a turkey feather and were asked to: (i) make a 
representative drawing of it, (2) diagram it, and (3) de- 
scribe it verbally. Twenty-four hours later, they were 
again required to draw a diagram of the feather from 
memory and also to answer certain questions about it 


(retention test). Each subject's performance on all five 
tests was scored independently by 10 judges in order to 
arrive at a final estimate of his score. The various correla- 
tions computed among these scores are reported below. 

Representative drawing and verbal description .271 

Representative drawing and diagramming .052 

Diagramming and verbal description .231 

Representative drawing and retention .022 

Verbal description and retention .234 

Diagramming from memory and retention .433 

As would be expected, the only positive correlations are 
those between diagramming (immediate or delayed), 
verbal description, and retention. These tasks have a 
good deal in common, since they all involve careful ana- 
lytic observation of the object. Little or no artistic talent 
is required in diagramming. The only task which implies 
drawing ability to any appreciable extent is representative 
drawing. This, it will be noted, shows very little correla- 
tion with the other tasks. All the correlations computed 
by Ayer with representative drawing are negative. Two 
are too low to indicate the presence of any relationship; 
the third, although also low, suggests the possibility that 
those subjects who rendered a good representative draw- 
ing may have overlooked certain details and concentrated 
chiefly on a general impressionistic observation. 

Mechanical f a^litod^&^ spmd^b jlity. 

Stenquist reports a correlation of .330 between the Sten- 
quist Assembling Test .and ..a, .,.,ccanp,Q$ite. t score, .froin^six 
verbal intelligence tests in a .group of 267,, seventh and 
eighth grade boys. Although reliably higher than zero, 
this correlation indicates only a very slight degree of re- 
lationship. The Stenquist Assembling Tests involve the 
construction of common mechanical objects such as a lock, 
bicycle bell, chain, and mouse trap, from given parts. 


In a very extensive and thorough investigation on 
mechanical aptitude conducted at the University of 
Minnesota (cf. 29)5 various correlations were computed 
between mechanical tests and intelligence. I-Q-'s were 
estimated from scores on the Otis Intelligence Test. ..The 
correlation between these I.Q/s and a mechanical aptitude 
battery, 1 composed exclusively of apparatus or manipula- 
tion tests, proved to be only .13 within a group of 100 
Junior High SchooTbo^^ ^ o bt a i nec i a correla- 

tion of .07 between a vocabulary test and the Minnesota 
Paper Form Board Test among 225 male college students. 
The latter is a paper-and-pencil test of the ability to 
handle spatial relations. Vocabulary tests, which measure 
the subject's understanding of word meanings, have been 
found to correlate so highly with the majority of common 
intelligence tests as to be practically interchangeable 
with them. From these examples, it is apparent that in 
large groups of subjects of different age and academic 
level, only a very low positive correlation exists between 
spatial or mechanical ability and the verbal type of in- 
telligence test. When the mechanical problems are pre- 
sented verbally, the correlations with intelligence tests 
are usually higher because of the common influence of the 
comprehension of verbal directions, knowledge of words, 
and general facility with verbal material. 

Of the special aptitudes suggested by case studies, only 
numerical ability remains to be examined. In spite of 
the indisputable presence of "mathematical prodigies" 
who are deficient in other respects, numerical ability has 
not usually be^n^k^^^^ 

metic tests are also frequently inciudedj^iot^ligence 
scalSsnCecent correlational analysis has demonstrated, 

1 A series of tests each of which is given an optimum weight and combined so 
as to give the best possible estimate of the trait measured. 


however, that the relationships between verbal and nu~ 
merical "tests* "are much' lower than those within either 
group "of Abilities. In many investigations, the correla- 
tions Between verbal and numerical tests were no higher 
than those between verbal tests and the various special 
aptitudes discussed above. 

obtained a correlation of .09 between a read- 
n test and a test of arithmetic reasoning 

in jajjroup of 140 seventh grade children. Schneck (30) 
tested 210 college men with 5 verbal and 4 numerical tests. 
The average of the correlations between all possible pairs 
of verbal tests was 4920; the corresponding average 
correlation for the numerical tests was .3383. When ver- 
bal and numerical tests were paired off, the average of 
the correlations so obtained was only .1441. Even this 
rather low positive correlation probably resulted from 
the fact that in at least one of the numerical tests, the 
problems were expressed in verbal terms, and in all of the 
tests the directions were given verbally. Anagtasij^) found 
a correlation of .or between arithmetic reasoning and 
vocabulary among 225 male college students. In a sub- 
sequent investigation by the same author (2) on 140 col- 
lege women, all possible correlations were computed 
among two verbal and two numerical tests. The correla- 
tion between the two verbal tests (vocabulary and analo- 
gies) was .65, and that between the two numerical tests 
(arithmetic reasoning and number series completion) .58. 
The average of four correlations obtained by pairing each 
of the verbal tests with each of the numerical was only 
.16. These various findings suggest that verbal and 

^WiMMIIMK*lmNWWMK. M ^^ * , fflMMSWlWl** #"!* "''*" ' '*"* * """' * "'*" ' **^*J"**'" 1W W*'*" 11 "'" ** > *"*' >** ' *"<" ' **" 

to be n^suri^,^ft.J*8p^ciaLapti- 

sense^ js as_,the Bother, tests, jdi^cussed 

No mention of personality traits has been made in this 


chapter. This is because the independence of personality 
and intellectual traits is now quite generally recognized. 
Emotional instability, for example, may be found over a 
wide range of intellectual levels. Insanity among highly 
gifted persons is not unknown. Extreme emotional dis- 
orders are perhaps not as common among the intellectu- 
ally ablest as among more mediocre individuals because 
the former can exert somewhat more control over social, 
economic, and other aspects of their environment and are 
therefore less frequently subjected to conflicts or frustra- 
tions. At the same time, certain forms of insanity are 
rare among low grade mental defectives because these 
individuals have too restricted a mental life to experience 
much stress or strain. 

^2!^J^^ a ^ so to ^ e y^T 

largely independent of ability. Criminals are not sig- 

nificantly differentiated from non-criminals in mtellegtual 
statusT ThTs waV demonstrated in an extensive investiga- 
tion by Mucdbis^ Alpha was 

admin^ in the 

penitentiaries of ^ five states. The distribution of fc the 
gco ^^TtEiJ^rou coincided ye^ closely with that^of the 
ar^^drpt from the same five states, j^mong^ juvenile 

delinquents, ^ajy^JS^^ * n ~ 

tellectuaf (deviation when thejsubjects are .j:jompared with 

a -iio53e]^ 

level^ET^ In the course of extensive 

experimentation with large groups of schoolchildren, 

vel T 1 22L22lS^ ons 

traits. The chifdren were tested in practical everyday 
situations and without their knowledge. Among the 

1 Separate investigations were also conducted on smaller groups of foreign- 
bora, Negro, and women prisoners. 


character traits investigated were lying, cheating, steal- 
ing, charity, cooperativeness, persistence, and inhibition. 
When the questionnaire type of test was employed (cf. 12), 
the correlations with intelligence were much higher, owing 
to the common dependence of such tests upon verbal 

The administration of tests of social traits or emotional 
instability to large groups also reveals little or no rela- 
tionship with intelligence- Thus, for example, no appre- 
ciable correlation has been found between intelligence 
test score and performance on the Colgate Tests of Emo- 
tional Outlets for measuring introversion and emotional 
instability. Within a group of 218 college students, a 
correlation of .02 was obtained between introversion scores 
and performance on the Thorndike Intelligence Test. 
The correlation between scores on the same intelligence 
test and number of neurotic symptoms proved to be .008 
among 203 male subjects and .12 among women (num- 
ber not stated). Thurstone (34) reports a correlation of 
.037 between scores on his Neurotic Inventory and the 
American Council of Education intelligence test among 
694 college freshmen. Bender (5) found a correlation of 
.0008 between scores on the same intelligence test and 
performance on the Allport Ascendance-Submission test 
in a group of 192 college sophomores. It is almost super- 
fluous to discuss correlations between intelligence and 
personality tests^ since in the construction of the latter a 
definite attempt is made to avoid an appreciable correlation 
'with intelligence. The assumption is implicit in techniques 
of personality test construction that the traits to be 
measured are independent of intellectual status. That 
these efforts have usually succeeded testifies to the sound- 
ness of the assumption. 



1. Anastasi, A. "A Group Factor in Immediate Memory,' 5 
Arch. Psychol, No. 120, 1930. Pp. 61. 

2. . "Further Studies on the Memory Factor," Arch. 

Psychol, No. 142, 1932. Pp. 60. 

3. Ayer, F. C. The Psychology of Drawing. Baltimore: War- 
wick and York, 1916. Pp. 186. 

4. Barr, M. W, "Some Notes on Echolalia," /. Nerv. Mental 
Diseases, 1898, 25, 20-30. 

5. Bender, I. E. "Ascendance-Submission in Relation to Cer- 
tain Other Factors in Personality," /. Abn. Psychol, 1928 
29, 23, I37-I43- 

6. Binet, A. Psychologie des grands calculateurs et joueurs 
d'echecs. Paris: Hachette, 1894. Pp.364. 

7. Bronner, A. F. The Psychology of Special Abilities and Dis- 
abilities. Boston: Little, Brown, 1919. Pp. 269. 

8. DeVoss, J. C. "Specialization of the Abilities of Gifted 
Children," in Genetic Studies of Genius, Terman, L. M., ed. 
(Vol. I, Ch. XII). Stanford Univ., Calif.: Stanford Univ. 
Press, 1925. Pp. 648. 

9. Fracker, C. C., and Howard, V. M. " Correlation between 
Intelligence and Musical Talent among University Stu- 
dents," Psychol Mon., 1928, 39, 157-161. 

to. Hartshorne, H., and May, M. A. Studies in Deceit. N. Y.: 

Macmillan, 1928. Book I, pp. 414; Book II, pp. 306. 
[I. Hartshorne, H., May, M. A., and Mailer, J. B. Studies in 

Service and Self-Control N. Y.: Macmillan, 1929. Pp. 559. 
[2. Hartshorne, H., May, M. A, and Shuttleworth, F. K. Studies 

in the Organization of Character. N. Y.: Macmillan, 1930. 

Pp. 503. 
[3. Hevner, K. "A Study of Tests for the Appreciation of 

Music," /. Appl Psychol, 1931, 15, S7$~5%3* 

14. Hoitsma, R. K., "Reliability and Relationships of the Col- 
gate Mental Hygiene Tests," /. Appl Psychol, 1925, 9, 


15. Hollingworth, H. L. Judging Human Character. N. Y.: 
Appleton, 1922. Pp. 268. 


16. Hollingworth, L. S. Special Talents and Defects. N. Y.: 
Macmillan, 1925. Pp. 216. 

17. . Gifted Children: Their Nature and Nurture. N. Y. : 

Macmillan, 1926. Pp. 374. 

18. . " The Musical Sensitivity of Children Who Test above 

135 I.Q.," J. Educ. PsychoL, 1926, 17, 95-109. 

19. Hull, C. L. "The Conversion of Test Scores into Series 
Which Shall Have Assigned Mean and Degree of Dis- 
persion," /. Appl. Psychol., 1922, 6, 298-300. 

20. . "Variability in Amount of Different Traits Possessed 

by the Individual,'' /. Educ. PsychoL, 1927, 18, 97-104. 

21. Kelley, T. L. Statistical Method. N. Y.: Macmillan, 1924. 
Pp. 390- 

22. . Crossroads in the Mind of Man. Stanford Univ., 

Calif.: Stanford Univ. Press, 1928. Pp. 238, 

23. Lindley, E. H., and Bryan, A. L. "An Arithmetical Prod- 
igy," Psychol. Rev., 1900, 7, 135. 

24. Manuel, H. T. A Study of Talent in Drawing. Bloomington, 
III: Public School Pub. Co., 1919. Pp. 152. 

25. Meier N. C. "^Esthetic Judgment as a Measure of Art 
Talent," Univ. Iowa Stud. : Series on Aims and Progress of 
Research, 1926, I, No. 19. Pp. 30. 

26. Minogue, B. M. "A Case of Secondary Mental Deficiency 
with Musical Talent," /. AppL PsychoL, 1923, 7, 349- 

27. Mitchell, F. D. "Mathematical Prodigies," Amer. J. 
Psychol.) 1907, 18, 61-143. 

28. Murchison, C. Criminal Intelligence. Worcester, Mass.: 
Clark Univ. Press, 1926. Pp. 291. 

29. Paterson, D. G., et al. Minnesota Mechanical Ability Tests. 
Minneapolis: Univ. Minn. Press, 1930. Pp. 586. 

30. Schneck, M. M. R. "The Measurement of Verbal and 
Numerical Abilities," Arch. PsychoL, No. 107, 1929. Pp. 49. 

31. Scripture, E. W. "Arithmetic Prodigies," Amer. J. PsychoL, 
1891, 4, 1-59. 

32. Slawson, J. The Delinquent Boy. Boston: Badger, 1926. 
Pp. 477. 


33. Stenquist, J. L. Measurements of Mechanical Ability. 
N..Y.: Teachers College, Columbia Univ., 1923. Pp. 101. 

34. Thurstone, L. L., and T. G. "A Neurotic Inventory," 
/. Soc. PsychoL, 1930, i, 3-30. 

35. Tredgold, A. F. Mental Deficiency. N. Y.: Wood, 1922. 
Pp. 569. 


The lack of relationship between intelligence test per- 
formance and several mental functions (cf. Ch. X) raises 
a question as to what constitutes "intelligence." It will 
be recalled that the original purpose of intelligence tests 
was to sample a large number of different abilities in 
order to arrive at an estimate of the subject's general 
level of performance. Insofar as A^mdiyjduaJ'.s, sjtanding 
in specific functions differs, , such,, a general , estimate is 
\nsatisfactory. It is apparent, however, that current in- 
telligence tests do not even furnish an adequate estimate 
of the average ability of the individual, since they are 
overweighted with certain functions and omit others. 
Thus in the non-language and performance tests of in- 
telligence, spatial aptitude plays the dominant role. 
Most paper-and-pencil tests, on the other hand, measure 
chiefly verbal ability and, to a slighter extent, numerical 

Sincej:heJ^ of test is by far the ,,most frequently 

emgjgxed^^the term "intelligQace'!, has come to" be used 
alm^st m ynonymously with verbal ability. Mental age 
on the Stanford-Binet, for example, has been found" to 
correHFe"^^^^ performance on the vo- 

caBHagr test of the scale (cf. 28). This finding led Terman 
to suggest that "a mental age based on the vocabulary 
score alone would not be far wrong in a large per cent of 
the cases" (30, p. 454). 

From another angle, most jntellig^c^^^ests ft maY be 
regarded as measures of scholastic aptitude, or abtiity^to 

""->" .-w,, i' J < ' ' ' *'"""*"" "''^wi- .%, np^^^M*, **., * 

*""""""'"* - -"*** *' " " 296 


succeedjn^our schools. This is illustrated particularly well 
by the procedure commonly followed in validating in- 
telligence tests. The term validity is used to denote the 
degree to which a test actually measures what it purports 
to measure. In the case of intelligence tests, validity is 
usually checked against school success as a criterion. 
Scores on the test are correlated with school grades or 
teachers' estimates of ability, and the higher these correla- 
tions the more valid the test is said to be. 

Some rather illuminating data on the relationship be- 
tween intelligence test performance and scholastic ability 
were brought together bjULdPkj*- (17, Ch. VIII). Avail- 
ing himself of material gathered by several investigators, 
Kelley presents correlations between scores on several 
intelligence tests and performance on the Stanford 
Achievement Test. The latter is a carefully constructed 
and standardized test covering several school subjects 
and was designed for use in place of ordinary school 
examinations. The correlation of this examination with 
the National Intelligence Test proved to be .66; with 
Otis Intermediate Test of Intelligence, the correlation 
was .79; and with Illinois General Intelligence Test, it was 
.71. These correlations are practically as high as those 
obtained when different intelligence tests are correlated 
with each other. Thus Stanford-Bract and National In- 
telligence Test correlated .84, National Intelligence Test 
and Terman Group Test .79, and Stanford-Binet and 
Terman Group Test .75. 

^ it would seem that "in- 

misleading, term 

. Recently, there has been a tendency eitKeFlo 
discard or to qualify the blanket term "intelligence" and 
to give more specific and more informative names to 
mental tests. Thus we find the Intelligence Scale CAVD, 


named after its four component parts. Completion, 
Arithmetic,. Vocabulary, and Directions; this test claims 
to measure no more than the "CAVD segment" of in- 
tellect (cf. 41). The Minnesota College Ability Test and 
the Scholastic Aptitude Test constructed by the College 
Entrance Examination Board are also examples of the 
explicit recognition of the specific nature of the measuring 
instrument. In the latter test, the subject is now given a 
separate score in the verbal and numerical parts (cf. 21), 
a procedure which testifies further to the influence of 
studies of trait relationship upon test construction and 
interpretation. Thus emphasis is shifting from indices of 
so-called general intelligence to concrete behavior traits 
and their interrelations. 

Such interrelationships among an individual's abilities 
are included under the rubric of mental organization. In 
investigating this problem, we are not only concerned 
with the establishment of the presence or absence of trait 
variations, but we are also interested in an exact formula- 
tion of the principles underlying the amount and di- 
rection of such variations. Through such an analysis, 
we shall be able to identify the basic components or uni- 
tary traits into which the individual's behavior may be 

Theories of mental organization are very old. As long 
as philosophers have discussed the nature of mind, they 
have proposed theories to explain how the "parts" of the 
mind were related or organized. With these speculations, 
however, we are not concerned. It is only since the appli- 
cation of mental tests and quantitative methods that the 
relationships among the varied responses of the individual 
could be measured. The more recent theories have been 
offered as interpretations of specific evidence and hence 
have a more objective foundation. 



The problem of mental organization was first placed 
upon an "empirical basis with the publication of Spear- 
man's 1904 article (26) in which were presented a theory 
and a. new method of investigation. 1 According to Spear- 
man^^Tzvo-Factor Theory, 2 all intellectual, activities 
have Jn fc common one fundamental function which, is 
caliei,tiie~~G^<?f al factor., or g. In addition, each activity 
has. Specific^? s factors. The s factors are exceedingly 
numerous and strictly specific to each activity of the 
individual. No two activities can share specific factors, 
by definition. Spearman argued that such a theory Js 
cpusktent with fi co^^ Thus the presence 

of different specifics in every' activity would explain the 
absence of perfect + i.oo correlations; no two activities, 
however much they may depend upon the g factor, are en- 
tirely free from specifics. The fact that most abilities are 
positively correlated, on the other hand, is attributed to 
the ubiquitous g. Different proportions of g and s in each 
activity wpulcl prpduce a wide range of, positive correla- 
tions,., all higher^ than zero and lower than i.oo. 

Itjollows from the Two-Factor theory that the aim of 
mental ^tegtmgLiliouldL |>;tQ m^as,nr^ the amount of each 
iBdisddjualls g. If this factor runs through all abilities, it 
furnishes the only basis of prediction of the subject's 
performance from one situation to another. It would be 
futile to measure specific factors, since each operates in 
only one activity. Accordingly, Spearman proposed that 
a single, tesvJugbJy'." 

1 Discussed below. 

2 For a discussion of the main points of this theory and its modifications, see 
27 and 28. 

3 Spearman employs the term "saturation" to denote the degree to which an 
activity depends upon the g factor. 


for the heterogeneous collection of items in intelligence 
scales. He suggested that tests dealing with abstract rela- 
tions, such. .-is; the analogies test, are the best single 
measures o*& and could therefore be employed for this 
purpose. '- -- ^,i 

In regard to the nature- of g, Spearman offers only ^tenta- 
tive suggestions/^ He^prpposes that g may be regarded j,s 
the genei^J ^'mental 'ef^rgy of the individual and the s 
factors asTtiie "engines" through which it operates, or 
the specific^ neurone Bitterns involved in each activity. 
This interpretation of | and s is not, however, an integral 
nor a basic part of the Two-Factor theory. It might be 
noted that -Spearman's g would also furnish a basis for 
the popul^ jnqtiqn of general intelligence. 

Even from the outset, Spearman realized that the Two- 
Factor theory must be qualified. When the activities 
compared are very similar, a certain degree of correla- 
tion may result over and above that attributable to the 
g factor. Thus in addition to the general and specific 
factors, there might be another intermediate class of 
factors, not so universal as g nor so, strictly specific as the 
j,, factors. Sj}ij s , facto^ ..which 4s. common, tp a group of 
activities but, not. to all, has been 'designated a, .group 
factor. In the early formulation of his theory, Spearman 
admitted the possibility of very narrow and negligibly 
small group factors, following subsequent investigations 
by.sey.ejal of his students, he included much broader, group 
factors of verbal ability and spatial or "practical" ability. 

Finally, on the basis of a series,, of studies,, additional 
general factQ^s )y,gre suggested. These include p (persevera- 
tTon), "o (oscillation) , and w (will), the last extending the 
theory to the field of personality traits. J[t has also been 
proposed by Spearman (cf. 28) that whereas i% ^ N rep repents 
tji total , amount of .mental energy at the subject's dis- 


posal, p may denote the inertia of such mental energy, 
-ag^^^i^rigtfeadiriess of its supply. Thus all three gen- 
eral factors may be but different manifestations or aspects 
of , the same fundamental factor. 

Spearman at present recognizes the presence of all 
three possible classes of factors, viz., general, group, and 
specific. The chief differentiating characteristic of his 
theory ..seems, to be its emphasis upon the g factor as, the 
predominant influence in correlation and its relegation 
of .grpup^factors to a position of minor importance. 

Thomson (31-34 and 7) has proposed a Sampling Theory 
of mental organization, which has undergone" 'lifEleTor* no 
change since its original formulation. Behavior, according 
to Thomson, depends upon a very large number of inde- 
pendent elements which he has occasionally identified 
with neurones or bonds between neurones. Any one 
activity of the individual depends upon or involves a 
particular sample or pattern of these elements. w Correla- 
tion^resuTts from the overlapping of different samples, of 
elements. There may thus be found any number of dif- 
ferent types of factors, varying from the specific, through 
group factors of differing extent, to the general. Thom- 
son has repeatedly illustrated, with data from dice throws, 1 
how various factor patterns could result from overlapping 
samples of independent elements. 

not due to i 

elementary abilities involved bu^jjjL^ 
aad,diJ^ .abilities. As a practical 

illustration of this, Thomson cites the well-known drop- 
ping out of unnecessary movements in the learning of a 
motor skill. 

1 Frequently employed in statistics as a means of obtaining purely random, or 
"chance" data. 


Thorndike's views on the relationships of mental traits 
seemTo^have run the gamut from extreme specificity to 
the opposite extreme of a single general factor. Thorn- 
dike's belief in strict specificity is ordinarily traced to his 
1909 article with Lay and Dean (40) in which, after 
reporting very low correlations between tests of sensory 
discrimination and estimates of intelligence, Thorndike 
concluded: "In general there is evidence of a complex 
set of bonds between the psychological equivalents of 
both what we call the formal side of thought and what 
we call its content, so that one is almost tempted to re- 
place Spearman's statement by the equally extravagant 
one that there is nothing whatever common to all mental 
functions, or to any part of them" (40, p. 368). 

Similarly, in the 1914 edition of Thorndike' s Educational 
^Psychology (35) appeared the following statements: 
c. . . the mind must be regarded not as a functional 
ticjut, nor even as a collection of a few general faculties 
2 fiich work irrespective of particular material, but 
f ac ther as a multitude of functions, each of which involves 
f a jntent as well as form, and so is related closely to only a 
r iew of its fellows, and to others with greater and greater 
degree of remoteness ... we need to bear in mind the 
singularity and relative independence of every mental 
process, the thoroughgoing specialization of the mind" 
(35? PP- 366-367). Thorndike also pointed out that "the 
circumstances of training would seem to sometimes in- 
tensify and sometimes weaken original relations" (p. 37 1 )- 
It will be noted that the possibility of narrow group 
factors is admitted even in these early statements, and 
the influence of environment in altering the organization 
of abilities is suggested. 

In 1921, following the analysis of intercorrelations 
among the subtests of Army Alpha and Army Beta, 


Thorndike (37) suggested the possibility of fairly broad 
group factors, including numerical and spatial aptitudes 
among others. In a symposium on intelligence and its 
measurement (38) appearing in the same year, he stated: 
" We know that, taking people as we find them, the ability 
measured by verbal tests is not the same as the ability 
measured by non-verbal tests; and there is reason to 
expect other similar specializations" (38, p. 126). But 
in this case specialization means group factors of fairly 
broad extent. At the same time, more emphasis is shifted 
to the environment as an influence which might produce 
specialization. This is illustrated by the following state- 
ment: "All of the above, 1 of course, concerns individuals 
as we find them, products of nature and nurture. Spear- 
man's doctrine might fit the original nature of intellect 
better. Certain factors, like ability to understand oral 
language, ability to read, ability to perceive objects in 
three dimensions, which occur to everybody as neither 
entering into all cognitive performances of a person nor 
entering into only a few very closely similar performances, 
might in original nature be absorbed into one unitary 
ability to learn" (38, p. 151). 

whereas "between^gg^ 


(36). It is doubtful, however, whether this analysis 
should be incorporated into a survey of Thorndike's basic 
theory since it was offered only as a practical suggestion 
to expedite testing. In any event, it falls in line with the 
above suggestions of broader group factors. 

In The Measurement of Intelligence (41), Thorndike 

1 Referring to specialization. 


swings all the way to a general factor theory with his 
Quantity Hypothesis. This^ hypothesis "asserts that in 
their deeper nature the higher forms of intellectual opera- 
tion are identical with mere association or connection 
forming, depending ozpon the same sort of physiological 
connection but requiring many more of them. By the same 
argument the person whose intellect is greater or higher 
or better than that of another person differs from him in 
having . . . simply a larger number of connections of 
the same sort" (41, p. 415). Thorndike also proposes 
that "we may be able for many "purposes to replace our 
measurement via a sample inventory of tasks, by a more or 
less direct measurement of C" (41, p. 422). By "C".he 
refers to the total number of connections which the indi- 
vidual can possibly have by original capacity. Attention 
is called to the fact that this hypothesis limits itself to the 
organization of original capacity, and that various other 
relationships may be environmentally produced. The chief 
difference between the Quantity Hypothesis and Spear- 
man's theory seems to be that in the former the number 
of possible connections is substituted for mental energy 
as the interpretation of the general factor. 1 

Lastly, we may consider what can conveniently be 
classified as Group Factor, u O& Multiply <wtor Theories. 
A group factor, it will be recalled, is one which is common 
to only a group of activities; it is narrower in extent than 
the general factor and broader than specifics. The publi- 
cation in 1928 of K^iley's Crossroads in the Mind of Man 
(18) paved the way for a large number of studies in quest 
of particular group factors. lili.dleya^ 
critical analysis of the methodology and data of Spear- 

1 Recently, Thorndike has again emphasized specialization, on the basis' of the 
current findings on trait relationships. He points out, for instance, that many of 
the recently proposed group factors "correspond interestingly" to "conceivable 
biological realities" (cf. 39). 


man, that the general factor is of relatively minor im- 
portance and can usually be attributed to the hetero- 
geneity 1 of the subjects and to the common verbal nature 
of the tests employed. If a residual general factor be 
found when these influences are ruled out, Kelley claimed 
that it would probably be very small and insignificant. 
The major relationships among tests he attributed to a 
relatively small number of broad group factors. Chief 
among these were manipulation of spatial relationships, 
facility with numbers, facility with verbal material, 
memory, and mental speed. 2 


It is not within the scope of this book to discuss the 
mathematical techniques which have been developed and 
refined for the analysis of trait relationships. This mate- 
rial is of too technical a nature to be of interest to the 
general reader* It is, however, necessary to learn some- 
thing of the general approach to the problem and of its 
limitations. The present section is intended to serve 
chiefly as an orientation for the proper understanding of 
the results to be subsequently reported. 

Fundamentally, all techniques for the study of mental 
organization are based upon the correlation coefficient. 
This measure indicates the degree of relationship between 
two sets of scores, or the extent to which each individual's 
performance in one test corresponds to his performance in 
another test. Correlation, however, cannot analyze the 

1 The influence of heterogeneity upon correlation coefficients will be discussed 
in the following section. 

2 Various modifications of group factor theories have appeared. Thurstone 
(42) identifies himself with some form of group factor theory, although he has 
been more concerned with the development of methods than with the formula- 
tion of a definite interpretation. Variations of group factor theory have also been 
proposed by Garrett (14), Hull (16), Meili (20), and Tryon (43). For a fuller 
description of each, see Anastasi (5), Ch. I. 


mutual interrelationships of a large number of variables. 
A correlation coefficient may indicate whether there is 
some factor common to a pair of tests, but it cannot show 
the presence of a single common factor through three, or 
four, or any larger number of tests. Let us suppose that 
all intercorrelations among three tests have been com- 
puted, with the following results: 1 

r 12 = .60 
fis = 49 

7*23 = -7 

Although all three correlations are positive and high, we 
cannot determine whether these three tests have one com- 
mon factor or several common factors among them. 
Test i might share one factor A with test 2, and a differ- 
ent factor B with test 3 ; a still different factor C might 
constitute the common element between tests 2 and 3 . 
It was Spearman (26) who, first demonstrated that 

coefficients it is 

L, an y 

traits. TheUin:^^ Spearman was the 

hierarchal arrangement of correlation coefficients. Accord- 
ing to this criterion, if it was possible to arrange all the 
ifftercorrctetiSris among a set of tests in such a way that 
they decreased consistently in size both aloag .the rows 
anH^Iong tfiFcoTumns oFtEe Stable, then the relationships 
an^ , entirely, in, terms of 

gjtnd^. This was a relatively crude "inspectional" method 
of determining hierarchy. Subsequently^ t^e computa- 
tion of intercolumnar correl^L^fT^w^B suggested as a 

p.^ ^-"""'"""'^^ I(MJ ((9!lf ,,,. i '"< " ',., , OQ'i 

conjsiiifiiik,, numenc*ff^tfex of hierarchy. The inter- 
columnar correlation 1 "* is simply the correlation between 
columns of correlation coefficients. A + i.oo intercolum- 

1 It is customary to denote the particular variables correlated by subscripts. 
Thus, ri2 is the correlation between test No. I and test No. 2. 


nar correlation would indicate a perfect hierarchal arrange- 
ment of the coefficients. 

Fifially,.Jthje.mtercoluin-nar correlation was replaced by 
thej^i, tt rx^tip^. The latter gets its name from the 
fact that the tests are considered in sets of four. For every 
four tests, or variables, we can compute three tetrad equa- 
tions as follows: 

^1234 = 7*12 X 7*34 ~ ?*13 X 7* 2 4 
^1243 = 7*12 X 7*34 7*14 X T^ 
^1342 = 7*13 X 7*24 7*14 X 7"23 

? rs ,h ave been, able, to prove ~ .tn^th^ 
.three tetrad equations are equal ; to 
single common factor Is sufficient to account 

d^^^ the four varkbles. 

This was a decided step forward from the simple cor- 
relation coefficient. It was now possible to analyze the 
interrelationships of any number of variables by comput- 
ing different sets of tetrads. The extension of the tetrad 
criterion beyond four variables can be easily demon- 
strated. Let us suppose that we have administered six 
tests to the same subjects. First, we compute the three 
tetrad equations with tests I, 2, 3, and 4. If all three tet- 
rads are equal to zero, we may conclude that the same 
factor which underlies tests I and 2 is also common to 
tests 3 and 4. Then if the tetrad criterion is likewise 
satisfied (i.e., all tetrads equal to zero) with tests i, 2, 5, 
and 6, we know that the factor common to I and 2 is 
identical with that common to 5 and 6. Hence the same 
factor must be common to all six variables. 

^^ ^k^JlE^ 

remained on 

1 Within their probable errors. 


speculation. In its specific application and interpretation, 
however, the tetrad criterion has been the target of much 
criticism. Its chief critic has probably been Thomson. 
The latter has repeatedly pointed out and demonstrated 
that the tetrad criterion can be satisfied without a g factor 
(cf. 31, 32, 33). The .satisfaction of the tetrad criterion 
merely indicates that the observed relationships among 
the given variables could be explained in terms of g and s. 
But they could also be accounted for by other factor 
patterns. In other words, tetrad equations can never dis- 
prove the possibility of alternative factor analyses of the 

The tetrad criterion is also inadequate in that it does 
not in itself indicate the magnitude or relative importance 
of the common factor in each variable. Similarly,, when 
the presence of group factors is demonstrated, 1 the weights 
of these factors in the various tests cannot be determined. 
Recently, more elaborate and exact procedures have been 
evolved for the direct analysis of any factor pattern. 
These methods have become known under the name of 
factor pattern analysis* Like^tetrads, they are ultimately 
Based upon certain relationships among correlation co- 
efficients. It is possible by, these, juelJiada^tg^arnve at 
thL ".weight" or "loading" of ^aph,,f actor jn^each of the 
^ap&bles. A sample of such a factor pattern analysis is 
shown below. 

In this factor pattern, the numbers below each factor 
show the weight of that factor in each test, or the degree 
to which performance in the test is attributable to that 
particular factor. Thus factor I has a large and positive 
weight in all four tests and is therefore a general factor 

1 I.e., when the tetrad equations are not equal to zero. 

2 Several different methods of factor analysis have been worked out; cf., e.g., 
Hotelling (15), Kelley (19), Thurstone (42). 




(After Hotelling, 15, p. 434) 


Factor I 

Factor II 

Factor III 

Factor IV 

Reading speed 





Reading power 





Arithmetic speed 



~. 37 6 


Arithmetic power 





Percentage of total var- 

iance attributable to 

each factor 





common to all of these tests. Factor II reveals a differ- 
entiation between verbal and arithmetic ability, since 
it has positive weights in the two arithmetic tests and 
negative weights in the verbal ones. Factor III has 
positive weights in the two power tests and negative 
weights in the two speed tests, thus suggesting a possible 
distinction between speed and deliberation, or careful- 
ness. The fourth factor is too small to be of any signifi- 
cance. The percentages given in the last row of the table 
indicate the relative importance of the four factors in all 
of the tests. Thus the first factor alone is sufficient to 
account for nearly one-half (46^%) of the relationships 
found among these four tests, the second factor for 36!%, 
the third for 13%, and the fourth for a negligible 4%. 

It should be kept in mind, that the same sort of gualifi- 
catioris made in the interpretation of tetrads applies to 
fSS^T'p^i^^^^^y^^'' In ho case is the possiDmty of 
alternative explanations precluded. As Thomson has 

pointed out, with Tny given body of ^ data, ^^JJjn 


twS^"^^ ,.on . psy^hjplggi^l, w S"ounds" 

(34, p. 185). Any set of intercorrelations can be analyzed 


into factors in an infinite" number of ways. In order to 
arrive at a determinate solution, certain "limiting condi- 
tions" must be imposed. The various current methods 
of factor analysis differ in their choice of limiting condi- 
tions^ prpbitulates. It might be noted, however, that in 
actual, practice the general results obtained by these 
djjfexeJiLmethods do not differ very significaiitly. 

In concluding this very brief survey of methodological 
problems, mention should be made of the widely discussed 
question ofjieterogeneiity. It has been repeatedly demon- 
strated, both empirically (cf. 10) and theoretically (cf. 13), 
that the size of a correlation coefficient is affected by the 
heterogeneity of the group of subjects upon whom the 
data were collected. The most obvious example is that 
of age heterogeneity. If the subjects range in age from 
3 to 15 years, a high positive correlation will be found 
between even such diverse characteristics as size of the 
great toe and Stanford-Binet mental age. The same two 
measures would yield a zero correlation within a homo- 
geneous age group such as, for example, lo-year-old chil- 
dren. N^does ? festewgeae^ 

tio^ coefficient. If a heterogeneous group composed of 
Chinese and Scandinavians were rated for height and for 
proficiency in the use of chopsticks, a fairly high negative 
correlation would be obtained between these two measures. 
The Chinese subjects would, in general, be shorter than 
the Scandinavians and definitely more adroit with chop- 
sticks. Within either group, however, we should scarcely 
expect any correlation between these two characteristics. 

w ;w^^ fcom- a -^narked degree of 


It is difficult to decide, however, just what 
constitutes a permissible degree of heterogeneity. Obvi- 
ously, all heterogeneity should not be eliminated, even 


if this were possible, since individual differences would 
thereby disappear and correlation would be meaningless. 
The desired degree of heterpg^eity:,, t must be determined 
arbitrarily and on the basis of the particular problem 
under investigation. It should always be remembered, 
hpj5^ver jw that a correlation coefficient, or any statistical 
measure derived therefrom, must be interpreted in th,e 
t^ of the particular group upon which it was obtained. 

Perhaps the most general finding of the numerous and 

on mental organization is the pjes- 
cj)i group factors of varying extent. ^wiUJpe recalled 
that all theories now admit the presence, of such factors, 
differing in the relative- emphasis which ,th^y 
em. There is scarcely a single well controlled 

study which has not revealed group factors of some sort. 
The in^ he ,organ- 

.relatively ,sm4LnumKez j?H^^ 

may copibiae in v-ar,iou^^w-ay&^m-aay.,,,Qne 

Of the group factors proposed by Kelley (18), definite 
evidence has been found for the verbal and 

factors (cf., e.g., 21, 24, 29). Sp^ial aptitude seems to*be 
a composite of more than one indepe^4wt^actor. The 
administfatiofi "of tEe'extensive series of Minnesota Me- 
chanical Aptitude Tests to groups of high school boys 
revealed a number of narrow group factors rather than 
one unitary factor in the ability to deal with spatial rela- 
tions (22). Other investigations have indicated the pres- 
ence of " practical intelligence " (i) which is predominant in 
.the performance type of intelligence test. In addition, inde- 
pendent factors of " mechanical aptitude " (8) and of " rou- 
tine manual aptitude" (9) have been tentatively established. 


The latter is found among motor skills and manipulatory 

In regard to a possible common factor of speed, the 
data are very conflicting. In general, there seems little 
basis for expecting an individual who is fast in one sort 
of mental activity to be proportionately fast in others. 
Speed of performance seems to be quite highly specific 
and to depend upon the nature of each particular task. 
When evidence is presented for the existence of an inde- 
pendent group factor (cf., e.g., 11), such a factor is very 
small and is cut across by numerous other group factors. 

Thq ,iame is true of memory. Individuals cannot be 
characterized as possessing a good memory or a poor 
memory, since they do not manifest uniform .powers of 
retention for different materials. A common factor through 
memory tests is found only when the tests are also similar 
in other respects. For example, if all are rote memory 
tests for relatively meaningless material and all the items 
are presented visually, then performance on such tests 
will show a common factor (cf. 2). In such cases, however, 
the same special devices or aids to memorization can be 
applied to all the tests. Thus if a subject evolves the de- 
vice of forcing a meaningful association into the material, 
this will help him on all the tests and thereby produce a 
certain uniformity of performance. But such is not the 
case when memory is tested in a variety of situations, 
including recall and recognition of logical material, rote 
memory for numbers and for letter combinations, memory 
for tones, etc. (cf. 3). 

In the measurement of personality, the same techniques 
of factor pattern analysis are being gradually introduced. 
Thus, for example, among the various items included in 
the Bernreuter Personality Inventory, two independent 
group factors, or "traits" have been identified (12). These 


have been tentatively described as sociability and self- 
confidence. Various investigators have undertaken factor 
pattern analyses of emotional stability, interests, and 
other phenomena of personality. Conclusions in regard 
to the organization of personality traits are still highly 
tentative, however, owing to the complex nature of the 
phenomena under investigation and to the relatively recent 
application of testing techniques to this field. 


The reader may have noticed that those aptitudes 
whidGTave^Been jhpwn be Jndep creator; differentiable 

by community, of mate^M 

content. Wh^njthe similarity among the tests was onejof 
"process, structure, orjorm, no clear-cut group factor could 
^^^^.^^^^^ them. Such^ was the case with speed 
and memory. Both may be tes ted . with any kind of ma- 

. . ^ 

and numerical factors are definitely linked,,, up with m^- 
^^^^^^^^^ factor will be found through verbal 
tests, regardless of what the subject is required to do 
with the words. The individual who ranks relatively 
high in verbal aptitude will excel in verbal memory, will 
be faster on a verbal test, more adept at perceiving rela- 
tions which are expressed linguistically, and so on. Thus 
content factors cut across the boundaries of form and 
seem to be the most potent determiners of uniformity of 
response. 1 

Direct evidence for this conclusion can be found in 

1 No fundamental differentiation between form and content is implied by this. 
The distinction is simply a convenient practical one. To be sure, a group factor 
is simply an index of relationship among the individual's responses to concrete 
stimuli. Similarity in that aspect of the situation which is commonly designated 
as "material" or "content" seems to exert more influence upon such relation- 
ships, however, than similarity in any other aspect. 


several studies which have employed tests differing both 
in form and in content. In an investigation with a wide 
variety of memory tests (3), for example, the specific 
materials of the tests were found to be much more effective 
in determining correlation than the methods of testing 
memory. Thus a logical recall and a logical recognition 
test, both involving prose passages, correlated .74 with 
each other; it should be noted that these two methods of 
testing memory are generally considered the most unlike. 
Similarly, the logical recall and recognition tests correlated 
.42 and .56, respectively, with a verbal analogies test. 
The correlations of these two memory tests with other 
memory tests, on the other hand, were much lower. 
Logical recognition correlated only ,23 with nonsense 
syllable recognition, for example, although both tests 
employed the same method of testing memory. 

In an investigation designed specifically to test the 
relative influence of " material" and "structure" in men- 
tal organization (25), more conclusive evidence for the 
same point was obtained. A series of 14 tests was admin- 
istered to 1 86 male college students. In respect to material, 
four of the tests were numerical, four spatial, and five 
verbal. At least three "structural patterns" were repre- 
sented, viz., analogies, generalizations, and construction; * 
each of these occurred in all three. types of material. A 
factor pattern analysis of the -intercorrelations .among 
these tests indicated; that .similarity of material was more 
influential than similarity of structure in producing -group 
factors.; ; . ..'.*." ' . \''. ':.''" 

It is intertW3guto compare tlie empirically discovered 
group* factors with the proposed, mental " faculties" of the 
medieval Scholastic philosophers, which, have found their 

1 Including such tests as sentence completion and number series completion, 
as well as spatial construction tests. 


way Into popular speech. Whereas the " faculty psycholo- 
Ssts^ spoke oFatteatipn, mSnory 3 ; judgment, reasoi^jng, 
ancTsTmilar mental processes, we now find group factors of 
verEaT, "numerical, and spatial aptitudes. The latter clas- 
sification Is one of content- the Scholastic was one of 


With the rapid accumulation of data on mental organ- 
ization, certain definite discrepancies have been brought 
to light. Rather than being stable and universal, trait 
' beeu fpuad tp.,vaj:y fcgin jpne^type of 
Sgearman called attention to these 

sjIB|ec?tg l a| Sgearman called attention to these 
differences in 1927, stating *that, "Another important 
influence upon^he saturation of an, a^Uity with. g- Appears 
to be, the class of person at issue" (27, p. 217). At this 
time, he also reported some data which suggested that 
among older as well as among brighter individuals, abilities 
were more specialized and the general factor played a 
relatively less dominant part. 

Although the data of earlier studies are somewhat 
conflicting, 1 recent and more adequately controlled in- 
vestigations have demonstrated a tendency for abilities 
to be more s^cm^e^^mori^ Bolder ^^^^j^ ttf ^mqp.g 
thqse 'i&skJ%kf* educational -levels.- TEus investigations on 
schoolchi^ the presence of^an 

appreciab^ (cf., e.g., 23). It is interesting 

* 'Jiaycs^mb^ of the ( studies , J>y^ Sjaearman^ 

.CC^iaB^I.-PR^ ^ 


Studies on college groups (cf., e.g., 2, 3, 24), on the other 
hand, have indicated a much more pronounced specificity, 

1 Cf . Anastasi (5) for a discussion of these data. 


with relatively narrow group factors. Recently , ^ some 
suggestive data have also been presented to show diverse 
factor patterns among various occupational groups (cf. 20). 
Certain interesting correspondences were noted between 
the nature of the occupational activities and the organiza- 
tion of the individual's abilities. 

Although these discrepancies originally led to contro- 
versy or confusion, they are now coming to be recognized 
as an important means of studying the nature of trait 
relationships. Thus two recent studies have been con- 
ducted with the explicit purpose of discovering age changes 
in mental organization. In one of these (14), three groups 
of schoolchildren, aged 9, 12, and 15 years, respectively, 
were given six memory tests as well as tests of motor 
speed and verbal, numerical, and spatial aptitudes. The 
intercorrelations among these tests tended to decrease 
with age, as is indicated by the average intercorrelations 
of .29, .26, and .14 obtained in the 9, 12, and 15 year 
groups, respectively. Factpjq p,atern analyses revealed a 
large general factor whose weight decreased, consistently 
from ages 9 to 15. 

In the secondjtudy (6), a single group ,Q .children were 
retested after a lapse of three years. 1 Eight tests, includ- 
ing verbal, numerical, and spatial materials, were admin- 
istered. ^Intercorrelations dropped from the first to the 
second testing^ this decrease being greater in the correla- 
tions between verbal and numerical tests than in those 
within either group. Factor pattern analyses corroborated 
these findings. At both age levels, a large general factor 
was found, but its magnitud^decteasjedx^ 
9 to 12. 

'**H.l, n ,) , I >< ' -fK 

x The initial data were collected in an earlier investigation (23) on mental 
organization with a group of 395 children. Of the latter, it was possible to obtain 
161 for retesting three years later. 


In both of these studies, the changes in mental organiza- 
tion may have resulted from a variety of conditions. 
The subjects differed in age, in general experience and 
training, and in academic level. It is therefore .impossible 
to determine what brought about the change in mental 
organization. It might be argued that mental organiza- 
tion undergoes a progressive and regular alteration with 
age. On the other hand, the variations observed may have 
resulted from environmental stimulation and in partic- 
ular from school instruction. The question can only be 
answered by an experimental approach. If the pattern of 
trait relationships can be experimentally altered, the in- 
fluence of environmental stimulation upon mental organ- 
ization will have been demonstrated. 

This was undertaken in a recent experiment by the 
writer (5). The essential aim of the study was the altera- 
tion of a factor pattern by a brief, relevant, interpolated 
experience. Five tests, including vocabulary, memory 
span for digits, verbal reasoning of the syllogistic type, 
code multiplication, and pattern analysis, 1 were admin- 
istered to 200 sixth grade schoolchildren. All subjects 
were then given instruction in the use of special tech- 
niques or devices which would facilitate performance on 
the last three tests only. This instruction was similar 
in its general nature to that received in the course of 
school work, as, for example, in the teaching of arithmetic 
operations, short-cuts of computation, etc. After a lapse 
of 13 days, parallel forms of all five tests were administered 
under exactly the same conditions as in the initial testing. 

age changes were reduce^ 

Ini^^SI^^i^IA janifbxm^ 
ves^g^itionon this problem. 

1 Predominantly a spatial ability test. 


For convenience in discussing the data, we shall refer 
to vocabulary and memory span, the two tests in which 
no instruction was received, as "non-instruction" tests; 
the remaining three tests will be referred to as "instruc- 
tion" tests. Ajzomgarison of the intercorrelations among 
the five variables in the initial and final testing showed 
practically no change in the correlation between the two 
"non-instruction" tests, a slight change in the correla- 
tions between "instruction" and "non-instruction" tests, 
a.nd a marked change in the correlations among the three 
"instruction" tests. Factor pattern analyses l revealed 
a wide variation from the initial to the final testing. An 
examination of the weights of each factor in the five 
tests before and after instruction suggested that the 
changes were such as would have been expected from the 
nature of the interpolated experience. 

All of the above investigations indicate,. that-" factors" 
cannot be regarded as fixed and immutable. Nor can 
they be interpreted in terms of underlying psychological 
entities. A "factor" is simply a mathematical statement 
of observed relationships among a group of concrete be- 
havior manifestations (cf. 4). And by relationship is 
meant nothing more than a tendency to concomitant 
variation. When we say that performance on two tasks 
is related, we mean simply that those individuals who 
excel in one tend also to excel in the other. To conclude 
any more than this from a factor pattern analysis is mere 


The experiment described in 

1 Computed by Hotelling's (15) method of principal components. 


the preceding section reproduced, in a highly condensed 
form, the type of experience to which the child is exposed 
in the course of school work and other everyday activities. 
It is therefore entirely possible that factor patterns are 
deteTmmecHn the first place by the nature of such exp^ri- 
divers e^J actgr^pattemgL .which . r h ave , been 

found in differjerit, populations, nifty, thus.,, have,, been ,<BJQ- 
vironmental],)L4H:Qduced. Insofar as the experiences of 
all of the groups employed in such studies have common 
features, certain fundamental similarities in their mental 
organization have been discovered. Insofar, however, 
as these experiences have varied from group to group, 
different patterns of mental organization were found. 
Thus a verj widespread, ..."yedxal... factor!', could _ easily 
^in 'our culture in. which, language plays so im- 
^rt' in a wide variety of fields. If there were 
n'aT system in which only woodcraft and poetry 
were taught, we might indeed find a " group factor" 
common to these two abilities and to no other. Those 
subjects who had spent more time and effort on their 
academic work would excel in both tasks, but not neces- 
sarily in other fields of activity. The experimental find- 
ings which have been reported furnish an illustration of 
how " group factors" might be produced or obliterated 
by the subject's experience. 

It also iollowsjt^ may vary with 

agV^SEm^e^g,^^^^^^^ 8 "&s" SK^^bjWt^s^x^ri- 
SnceTTccMtiuiate throughout his life, certain alterations 
in the pattern of mental organization will take place. 
The relationships of performance in the same or similar 
situations will not remain constant over a long period of 
time. If the lapse of time is short, the influence of the 
intervening experience may be too slight to produce an 
appreciable difference in factor pattern. Over a long 


period, however, the cumulative effect will become ap- 
parent, as in the comparison of children with adults. 

In summary, it would seem that the relationships 
amoi^'^Tndividuars performance on a number of tests 
at any one time may be explained in terms of a small 
number of independent unitary factors* Under existing 
cultural "conditions, a certain degree of uniformity of 
factoif pattern's is found because of a general environ- 
mental uniformity. Traditional educational curricula and 
vocational classifications have probably contributed much 
towards this uniformity. Thus in the young schoolchild, 
we find a large general factor through all types of activities 
which are taught in our schools, the so-called "higher cen- 
tal processes." As the child grows older and specialization 
of function is encouraged, certain culturally determined 
differentiations appear. "Qrcmp factors" are produced 

w-nuu^u. *-"*'> - ' '" ' ' , < . "f" * , n , ^""" 1 a ^^ Jfc'Jtt 

in linguistic, mathematical, mechanical, and possibly 
other functions. These f actors,, ., however,, are only a 
mathematical statement or conceptual simplification of 
the observed relations among concrete responses. And 
as such they may be expected to shift from time to time 
in the same subjects or from one population to another 
because of varying experiences. 

Thus the role of environment is again forcefully demon- 
strated. In view of the dependence of the individual's 
behavioral development upon environmental stimulation, 
it is not surprising to find that the relationships among 
various classes of behavior are also environmentally de- 
termined . Thejais^^ of 
trait relationship could ^arcely,,,^ 
^traffr tKeniselves "have been found ,^tp,. Jbo^Sfi 
influenced by experiential 



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In Part I we surveyed some of the major problems and 
findings on individual differences and attempted to un- 
ravel the factors and conditions which produce variation 
from one person to another. With this background, we 
may now turn to an examination of certain groups into 
which individuals are commonly classified. Such groupings 
have been built up through social and cultural traditions 
and illustrate the general tendency to employ rigid cate- 
gories and sharp divisions. Thus individuals are popularly 
classed into the normal and the abnormal,, the genius, the 
feebleminded, the insane, the neurotic. Psychological 
differences are expected, or at least sought, between the 
sexes or among nations or "races." Many other groupings 
can likewise be construed. A person can be classified, for 
example, in regard to religion, political affiliation, or even 
place of residence. Psychological differences might be 
expected between urban and rural populations, or between 
groups inhabiting regions of different geographical char- 
acter, such as mountainous or flat, inland or coastal, cold 
or warm. 

These various groupings, like all rigid classifications of 
individuals, are arbitrary and artificial. In all behavioral 
traits, people are distributed according to the normal bell- 
shaped curve and cannot be assigned to distinct cate- 
gories. When the distributions of any two biologically or 

O **.*M.S"^ v**At <JjU/5i^lrf^4Sa4f Jl,n*3.*ll(4 "HK-VdfSuf'Si-iWi 'wiswS 




averages of doubtful practical significance. In such com- 
parisons, the difference between the averages is far smaller 
than the range of difference within either group. In the 
study of individuals, the only proper unit is the individual. 
There is no short-cut to the understanding of people, no 
possibility of learning the behavioral peculiarities of a few 
broad groups into which any individual could then be 
conveniently pigeon-holed. 

The multiple and complex determination of the in- 
dividual's behavioral development should in itself make 
us skeptical regarding any simple systems of characteriz- 
ing people. Yet it is an all too common practice to expect 
an individual to be dependable, or shiftless, or dull, or 
excitable, or poor in mechanics, or to ascribe to him 
dozens of similar characteristics, simply from the knowl- 
edge that such a person is a man or a woman, or that he 
belongs to a particular "race" or nation. 

It is partly to clarify these very muddled popular no- 
tions that the empirical study of group differences ought 
to be undertaken. To be sure, a careful examination of 
the principles underlying individual variation in general 
should suffice to show the fallacies inherent in many 
popular claims regarding group differences. But when 
beliefs are as deep-rooted and emotionally tinged as those 
governing many group relations, they are not easily dis- 
lodged. Direct evidence on the nature of group differences 
is more convincing than deductions from generally estab- 
lished principles. 

From a more theoretical point of view, the analysis of 
group differences is a valuable adjunct to the investiga- 
tion of individual differences in general. The existence of 
culturally diverse groups may be regarded as furnishing a 
natural experiment in the production of human variabil- 
ity. If psychological differences among groups are in- 


vestigated with reference to the factors which brought 
them about, the understanding of individual differences 
will have been considerably furthered. 

In the present analysis of group differences, we shall be 
more concerned with fundamental concepts and method- 
ological issues than with a cataloguing of results. The 
latter have little meaning unless critically evaluated. The 
data on group differences are difficult to interpret and have 
frequently led to opposite conclusions in the hands of 
different writers. It is of fundamental importance, there- 
fore, that the special difficulties inherent in group com- 
parisons be clearly realized and that the necessary cautions 
and controls be applied before making any generaliza- 
tions. With a clear understanding of the problem, the 
reader will be in a position to make his own interpretation 
of any data which he may come across. And he will also 
be able to guard against the pernicious habit of over- 
hasty generalization and to detect the fallacies in errone- 
ous statements with which he may be confronted. Ob- 
jective and critical habits of thinking are more urgently 
needed in the field of group differences than are randomly 
gathered data. Of the latter there is a sizable accumula- 
tion, while the former are all too frequently lacking even 
in supposedly scientific discussions. 



From the earliest periods of 

humanlnstory, we find instances of conspicuous deviates 
whom we should now regard as feebleminded or insane. 1 
Such individuals were generally considered to be distinct 
beings, either representing a lower order of humanity or 

1 For a historical survey of conceptions and treatment of insanity and feeble- 
mindedness, see Farrar (9) and Hollingworth (14), Chs. 2 and 3. 


"possessed" by spirits. These spirits were usually con- 
sidered to be evil, although in certain cases they were 
looked upon as gods. This demonological view was par- 
ticularly prevalent during the Dark Ages and reflects the 
influence of Christianity upon the thought of the period. 
At this time, it was Satan who was thought to " possess" 
the demented person. Such a condition was supposed to 
be visited upon the individual either as a punishment for 
his sins or as an ordeal to test his moral fortitude and 
religious faith. Thus many persons who were subsequently 
sanctified by the church experienced epileptic seizures, 
hysterical paralyses or anaesthesias, hallucinations, para- 
noid delusions, and similar well known symptoms of in- 
sanity. The treatment of mental disorders consisted of 
exorcism, physical abuse, or veneration, depending upon 
the particular theological doctrine which happened to be 
current or upon the specific circumstances of the subject's 

The medical view of mental disorders, on the other hand, 
was put forth as early as the fifth century B.C. by the Greek 
physician, Hippocrates. The latter proposed that mental 
disorders result from disease or injury to the brain. He 
also wrote extensively on various classes of mental dis- 
orders and their probable physical bases. For many cen- 
turies, the doctrines of Hippocrates were accepted un- 
questionably. They were suppressed during the Dark 
Ages, together with most of the. scientific knowledge of 
the Greeks, but were again resumed with the revival of 
scientific interest and the development of anatomy and 
physiology during the Renaissance. The medical con- 
ception of mental abnormalities is still prevalent at pres- 
ent, especially among psychiatrists. 1 

The psychological study of the abnormal is of relatively 

1 A psychiatrist is a physician who specializes in mental disorders. 


recent date. Its approach to the problem Is through a 
direct study of behavior. Behavioral disorders are explained 
in terms of behavioral principles, rather than by reference 
to some other realm or class of phenomena. Abnormal 
psychology is an empirical and direct study of extreme 
deviations in behavioral traits. As such it has been re- 
garded as a branch of differential psychology. 


The term abnormal, which means literally "away from 
the norm/' has been used to cover at least three distinct 
concepts. 1 First, we may consider the anti-normative view 
which regards as abnormal any deviation from the ideal 
or perfect condition. The norm in such a case is a goal or 
desideratum to be approximated by the existing conditions. 
To be "normal, 35 according to this view, would be the 
exception rather than the rule. Such a use of the terms 
normal and abnormal is illustrated by a number of com- 
mon expressions. To say that a person is one of the 
"lucky few" who have a normal skin or normal teeth, for 
example, implies an identification of normality with free- 
dom from defects or other imperfections. Or to assert 
that few can remain normal under the stress and strain 
of modern life suggests that normality is an ideal state of 
perfect composure and stability. 

A second view identifies abnormality with pathological 
or dangerous conditions. This usage is particularly com- 
mon in medicine. To be- classed as abnormal in this sense 
would have distinctly undesirable connotations. Such a 
view may be regarded- as an adaptation of the anti- 
normative concept to meet practical and social require- 
ments. The abnormal still represents a deviation from a 
perfect condition, but the deviation is now so great as to 

1 Cf. Hollingworth (14) and Foley (n). 


present practical difficulties. The condition requires action 
of some sort for the protection either of the individual or 
of society. Thus a person who exhibits a few mild neurotic 
symptoms, such as a compulsion to avoid stepping on the 
cracks in the sidewalk or a slight twitching of the forehead, 
may elicit the remark: "a bit queer, yes but not serious 
nothing really abnormal about him." But let such an in- 
dividual become so depressed over an imagined or exag- 
gerated wrong that his work must be discontinued, or let 
him threaten a suspected enemy with physical violence, 
and he will immediately earn the appellation " abnormal." 
According to this view, only a very small number of in- 
dividuals are abnormal, the large majority being indis- 
criminately classified as normal. 

Both of the above views necessitate an arbitrary norm 
or standard. In the first, the norm is a theoretical ideal, in 
the latter a practical criterion of individual and social 
survival. A more objective and empirical approach to, the 
problem is furnished by a purely statistical, concept of ab- 
normality. The norm in this case is the average. It is the 
usual and most common condition. The abnormal is the 
unusual, the relatively infrequent. The more infrequent a 
condition, furthermore, the more abnormal it is con- 
sidered. Many conditions classed as abnormal in the 
pathological sense would also be regarded as statistically 
abnormal because of their relative rarity. On the other 
hand, the majority of those individuals classed as ab- 
normal according to the anti-normative view would be 
considered normal, since they constitute the large, inter- 
mediate, and most representative segment of the popula- 
tion. Similarly, those who approximate the ideal or per- 
fect state too closely would now be regarded as abnormal, 
since they deviate significantly from the ordinary, average 


It follows from the statistical view that the abnormal 
may be either inferior or superior to the normal. The 
abnormal corresponds simply to the two ends of the nor- 
mal distribution curve. Since the curve is symmetrical, 
the superior deviate is just as abnormal as the inferior, in 
the sense that he is equally far from the norm. It is 
apparent that this is the only sense in which abnormality 
can be objectively determined and measured. To speak 
of inferiority and superiority implies evaluation in terms 
of specific biological and cultural requirements. Such 
evaluation is characterized by a certain degree of imper- 
manence and subjectivity which often confuse the prob- 
lem. A purely statistical concept of abnormality, on the 
other hand, limits itself to an incontrovertible and em- 
pirical criterion. 

It is in the statistical sense that the term abnormal will 
be employed in the present discussion. In respect to any 
specific situation, the abnormal will be further subdivided 
into the subnormal and the super-normal. The present 
chapter will be concerned with the subnormal deviates. 
The super-normal will be considered in the following chap- 
ter on "genius." These two groups of extreme deviates 
should be constantly viewed in their proper perspective, as 
opposite ends of a continuous distribution curve. 

It is noteworthy that the terms abnormal and sub- 
normal are frequently employed interchangeably. In 
everyday speech, it has become almost impossible to use 
the word abnormal in its innocuous etymological sense. 
To congratulate a great scientist upon a recent discovery 
by informing him that we consider him extremely ab- 
normal would probably be a breach of etiquette. Nor is 
this confusion restricted to popular usage. Most text- 
books on abnormal psychology, for example, deal exclu- 
sively with the subnormal, A few make brief mention of 


the logical need for including "genius" in this category. 
Having acknowledged this fact, however, they then devote 
all subsequent chapters to the subnormal 

The identification of abnormality with subnormality 
may result in part from the influence of the anti-normative 
and pathological views. Such a confusion of terms also 
offers an interesting commentary upon human thought. It 
is an all too common practice to regard as inferior what- 
ever differs from oneself. Mutual racial prejudices are a 
good example of this tendency. The strange paradox that 
several distinct groups may each regard themselves as 
superior to all the others is attributable to this human 
characteristic. To be too different from oneself must 
surely imply some sort of defect, otherwise one's self- 
respect would be too seriously impaired! 


Feeblemindedness represents the lower end of the dis- 
tribution of intelligence. It is characterized by intellectual 
rather than emotional defect. The term feeblemindedness 
is not used, however, to cover deficiency in any ability. 
Thus an individual may be far below average in music, 
drawing, or even mechanical aptitude, and still be re- 
garded as intellectually normal. 

nateiA , d&jiciency. *only ,in those abilities, 
essential /pr suvvival .in our cultural , milieu . 

As was indicated in the preceding chapter, verbal ability 
probably plays the dominant role in our conception of 
feeblemindedness. Linguistic aptitude has, often been ex- 
plicitly accepted as a criterion of mental deficiency. Thus 
Binet and Simon (4) wrote: "An idiot is a person who is 
not able to communicate with his fellows by means of 
language. He does not talk at all and does not under- 
stand." Similarly, Esquirol (cf. 14, p. 165) distinguished 


between three levels of feeblemindedness : (a) those mak- 
ing cries only; (b) those using monosyllables; (c) those 
using short phrases but not elaborate speech. Another 
classification which is still widely quoted (cf. 14, pp. 165- 
166) is that between: (a) Idiots, who are incapable of 
spoken language, and are limited, to gestures; (b) Im- 
beciles, who are able to understand and employ spoken 
language; and (c) Morons, who are capable of acquiring 
also written language, but have difficulty with the more 
complex verbal and abstract concepts. 

Feeblemindedness has been described from many points 
oj^vjewrj Probably the most common definitions are the 
sociological, or economic, and the psychometric. A widely 
quoted schema of classification adopted in 1908 by the 
Royal Commission on the Feebleminded, of Great Britain 
(5), illustrates the sociological conception. This classifica- 
tion recognizes three grades of feeblemindedness, charac- 
terized as follows : 

1. Idiot (low grade amentia) "A person so deeply defective 
from birth or from an early age that he is unable to guard 
himself against common physical dangers." 

2. Imbecile (middle grade amentia) "One who, by reason 
of mental defect existing from birth or from an early age, 
is incapable of earning his own living, but is capable of 
guarding himself against common physical dangers." 

3. Moron 1 (high grade amentia) "One who is capable of 
earning a living under favorable circumstances, but who 
is incapable, from mental defect existing from birth or 
from an early age, (a) of competing on equal terms with 
his normal fellows, (b) of managing his affairs and himself 
with ordinary prudence." 

1 In England, the term "feebleminded" refers to the high grade aments, and 
"amentia" is used as a general term to cover all degrees of mental deficiency. 
The term "moron" has been substituted for "feebleminded" in the above defini- 
tion, in accordance with the more familiar American usage. 


The psychometric classification is more common among 
mental testers and admits of more quantitative definition. 1 
When applied only to adults, the differentiation is often 
made on the basis of mental age. Thus an adult whose 
mental age is three years or less is usually regarded as an 
idiot; between three and seven is the imbecile level; 
morons fall above a mental age of seven but fail to reach 
the average adult level. To make the classification appli- 
cable to children as well as adults, the limits have been 
expressed in terms of LQ. Terman's classification (23, 
p. 79) is probably the most widely employed and has been 
reproduced below. 

Designation LQ. 

Dullness, rarely classifiable as feeblemindedness 80-90 
Borderline deficiency, sometimes classifiable as dull- 
ness, often as feeblemindedness 70-80 
Moron 50-70 
Imbecile 20-50 
Idiot below 20 

It should be borne in mind that these distinctions are 
purely arbitrary and are made only for practical con- 
venience. There is no sharp dividing line either between 
the normal and the feebleminded, or between the various 
"levels" of feeblemindedness. The intellectual differences 
are of degree only and form a continuous gradation, al- 
though the social effects may differ qualitatively. 

The feebleminded have also been classified in respect to 
physical characteristics. According to the early medical 
conceptions, feeblemindedness was a disease which was 
expected to show physical as well as mental symptoms. 
The percentage of feebleminded persons who present a 
distinct morphological picture proved, however, to be 
very small. 1 The large remaining majority had to be given 

1 Hollingworth, for example, estimates the number as only 10% (14, p. 159). 


the unrevealing appellation of " simple amentia." The 
major clinical varieties of feeblemindedness which have 
been differentiated include microcephaly, hydrocephaly, 
cretinism, and Mongolism. 

The.^ microcephalic has an abnormally small, pointed 
skull, producing a characteristic "sugar-loaf" appearance. 
'TEoTiydirocep'halic has a very large skull and an excessive 

fluid intervening between the 
-the brain, Th&.crftin has already been described 
in a different connection (cf. Ch. VIII). He is easily 

.. physique, coarse thick skin, Ipss 

ofjiair,^and other physical characteristics. This condition 
has been definitely linked with a thyroid deficiency and 
has been frequently relieved by repeated administration of 
thyroid extract in early childhood. Mongolism^ acquired 
its name from a certain facial resemblance to the Mon- 
golian race. This ^similarity, it should be mentioned, is 
quite superficial and slight. The peculiar, narrow, slanting 
"eyes"" cUar acteris tic of this type of ament were chiefly 
responsible for the alleged resemblance to the Mongolian 
face. This condition can also be distinguished by the shape 
of the skull and certain peculiarities of the tongue. 1 

Apart fromjhej;elj^ 
fiable into these special clinical varieties, the 

~~~***^~~*. T "3f '(a>%-A 1 w* n1 * rP '' s ' ' f " m "" " ' 

are noT3S^^fferentiat;ed from^mal i 
traits.^Data relevant to this question have already been 
presented in Chapter VIII. It will be recalled that in such 
physical measures as height and weight, the differences 
between the averages of normal and feebleminded sub- 
jects were small and the overlapping large. It is true that 
in practically every comparison the feebleminded are con- 

1 For a comprehensive survey of these clinical varieties as well as the charac- 
teristics of the feebleminded in general, the reader is referred to Tredgold (25) ; 
see also 22, for a discussion of feeblemindedness in children. 



sistently below normal in physical as well as mental 
traits (cf., e.g., 8, 20). But in evaluating these findings, 
we must bear in mind the influence of social and economic 
level upon both physical and mental development. In 
dealing with institutional cases, furthermore, the operation 
of selective factors must be taken into account. 1 

It has been repeatedly demonstrated that the feeble- 
minded are not 'equally deficient in all functions and that 
the degree of their inferiority increases as we go , from 
sinvgle^sensoiy arid .motor traits to, complex intellectual 
processes, and especially "symbolic" activities (cf. 6, 14, 
20). 3>Torsworthy ? for example, found that the percentage 
of feebleminded subjects out of a group of 157 who reached 
or exceeded the median score of normal groups was much 
greater in the simple sensory arid perceptual functions 
thaji in abstract verbal tests. The same was true when the 
percentages who reached or exceeded the i P.E. point 
rather than the median were compared. 2 The data for 
both types of comparison are presented below (cf. 20, p. 68). 

Function Tested 

Comparison of weights 
Cancelling A's 

Cancelling words containing a and t 
Memory for unrelated words 
Memory for related words 
Association : part-whole 
Association: genus-species 
Association: opposites, form I 
Association: opposites, form 2 

Percentage of Feebleminded 
Subjects Who Reached or Exceeded: 

Median of I P.E. of 

Normal Group Normal Group 

18 ' 28 

9 18 

I 14 

6 18 

5 19 

9 17 

9 16 

o 0.9 

o i 

achevments of 

1 Cf. Ch. VIII for a discussion of both points. 

2 In a normal group, 75% of the cases would reach or exceed I P.E. 


subjects. Performance in each subject was expressed as 
a ratio of the average achievement expected from normal 
children of the same age. These ratios are reproduced 

School Subject Educational Ratio 

Spelling .460 

Reading comprehension .489 

Composition .514 

Reading: accuracy and speed .534 

Subtraction .534 

Division .553 

Addition .565 

Multiplication .589 

Writing: speed and quality .609 

Drawing .649 

Handwork .697 

It is apparent from this analysis of abilities along vari- 

^ >^ ou p are m ost de- 

Bartask's. In arithmetic, their performance is 
intermediate, and in activities involving mechanical apti- 
tude or motor skill, they are closest to the norm. This 
does not mean, however, that such a hierarchy of defi- 
ciency exists within the individual feebleminded person. 
The same result might follow if there were more feeble- 
minded persons deficient in verbal ability, fewer deficient 
in arithmetic ability, and fewest in mechanical or motor 
aptitudes. THe relationship between such group averages 
depends not only upon the relative amount of inferiority 
displayed by each individual, but also upon the number 
of persons who are inferior. Since verbal aptitude plays 
such a large part in the criterion of feeblemindedness, 
almost all persons in a feebleminded group will be defi- 
nitely below normal in this trait. This consistent inferior- 
ity will of course produce a very low group average in 
verbal traits. 


In arithmetic aptitude, many will be below average, 
some may be normal, and a few even superior. The slight 
positive correlation between performance on arithmetic 
and verbal tests, as well as the fact that arithmetic tests 
are frequently included in scales of "general intelligence," 
would lead us to expect the majority, but not all, feeble- 
minded subjects to be below the norms in arithmetic 
aptitude. This would result in a group average higher 
than that in verbal traits, but still considerably below 

In tasks involving motor skills or aptitude in mechanics, 
music, or pictorial art, we should expect the feebleminded 
to be distributed very similarly to a normal group, since 
these traits show little, or no correlation with verbal ability 
or intelligence test performance. The majority would in 
this case be normal, only a small number inferior, and a 
few superior. As a result, the status of the group as a 
whole would be only slightly below normal. Thus it is 
apparent , that the,hlerarchy of deficiency usually found la 
feebleminded groups is # result of the culturally imposed 
criterion of feeblemindedness as well as the organization 
of, abilities. 


Insanity consists of a marked deviation in emotional 
or other personality traits. The individual, although in- 
tellectually normal or even superior, is unable to make a 
satisfactory adjustment because of serious personality 
disorders. Thus he may have delusions of persecution, 
which make him suspect all with whom he comes into 
contact of plotting against him, or delusions of grandeur, 
in which he believes himself to be Napoleon or some other 
favorite character. Such symptoms are classified under 
paranoia. Or he may develop such extreme introverted 


tendencies as to lose all contact with his fellow-beings and 
with occurrences about him, as in dementia prtecox. His 
symptoms may consist of recurrent periods of extreme 
depression and excitement, as in manic-depressive insan- 
ity. These examples will suffice to show the varied forms 
which insanity may take. We are not here concerned with 
a classification of insanities, or psychoses, into the common 
clinical varieties, nor with an enumeration of symptoms. 
This material can be found in any standard textbook of 
psychiatry and in many books on abnormal psychology 
(cf., e.g., 17, i8 5 19). We are concerned only with the gen- 
eral psychological nature of such psychoses. 

In the first place, insanity is not to be confused with 
feeblemindedness. The insane are recruited from all in- 
tellectual levels. Many psychotics fall within the normal 
range of intelligence. Instances are not unknown among 
the highly gifted. And likewise, insanity may occur in 
feebleminded individuals, although for some psychoses, 
such as paranoia, a certain degree of complexity of men- 
tal life seems to be required. A number of psychotic con- 
ditions, such as dementia prsecox, lead to intellectual 
deterioration, but there are others, such as paranoia, in 
which the subject may suffer no impairment of abilities. 

As in the case of feeblemindedness, there is no sharp 
dividing line between insanity and normality. Sharp dis- 
tinctions are made for practical purposes of confinement, 
treatment, and similar reasons, but close examination 
reveals a continuous, unbroken gradation from the thor- 
oughly well-adjusted person to the conspicuously insane. 
Psychotic symptoms differ only in degree from the behav- 
ioral peculiarities of the normal individual. From the 
blissful optimist who trusts implicitly whomever he meets 
to the paranoiac who believes that the stranger who acci- 
dentally brushes against him is plotting his demise, there 


are all degrees of "suspiciousness." The same may be said 
of all other characteristics of the insane. A good example 
of this is the familiar case of the student who, upon read- 
ing a manual of psychiatry or attending a course in ab- 
normal psychology, believes himself to be afflicted with 
each form of psychosis in turn. Most of us can discover 
in ourselves at least one characteristic of many types of 
insanity, in mild form. It is not normal, in the statistical 
sense, to be entirely free from all such slight peculiarities. 

A fundamental distinction from the viewpoint of the 
psychologist is that between organic and functional dis- 
orders. Briefly, organic disturbances are those which can 
be definitely attributed to a structural deficiency. In 
functional disorders, on the other hand, there seems to be 
only a faulty operation or deficient action of apparently 
normal structures. 1 Thus general paresis has been defi- 
nitely traced to the influence of syphilitic infection upon 
the nervous system; a group of psychoses have been shown 
to develop from excessive use of alcohol or drugs; injuries, 
or lesions, to certain parts of the brain or lower nerve 
centers lead to characteristic behavioral deficiencies. There 
remain, however, a large number of psychotic conditions 
for which no physical basis has been discovered. Some 
claim that the physical concomitants of such behavioral 
disorders are only undiscovered and that ultimately all 
will be adequately explained in structural terms. 2 

There is a growing conviction, however, especially 

1 This distinction, although generally employed only with reference to per- 
sonality disorders, could be applied equally well to feeblemindedness. Cretinism, 
for example, represents an organic mental deficiency resulting from physical dis- 
orders. In nearly 90% of feebleminded cases, however, no structural deficiency 
can be discovered and the disturbance might be regarded as functional. In a few 
instances, as in isolation amentia, the functional nature of the disorder is clearly 

2 For a discussion of various forms of insanity from this point of view, see 
Moss and Hunt (19). 


among psychologists, that these disorders may be purely 
functional in their origin and involve no structural im- 
pairment. If this be the case, we should seek the causes 
of psychotic conditions in the mechanism of learning and 
in the environmental conditions which have surrounded 
the individual. 1 This question is still a highly controver- 
sial one to which no final answer can be given as yet. 

That many behavioral disorders are functional can, 
however, be clearly demonstrated. A number of tests 
have been suggested for diagnosing the functional nature 
of several types of symptoms (cf. 14, Ch. 10). Thus func- 
tional disorders are more often intermittent and occasional 
than organic disorders and may depend upon the presence 
of a specific situation or stimulus. The symptom may only 
be manifested, for example, in the presence of certain 
individuals or in a particular locality. Functional dis- 
orders are also more variable, exhibiting more individual 
idiosyncracy from one case to another. Functional symp- 
toms of a motor or sensory nature can usually be detected 
because of their anatomical impossibility. The so-called 
"stocking and glove" anaesthesia, for example, is a loss of 
sensitivity in regions which are unitary only in popular 
thought, but do not correspond to any neurologically pos- 
sible division. In certain types of symptoms, special 
methods of examination, employing unusual situations 
unknown to the subject, will also reveal the functional 
nature of the disorder. 

Finally, a very striking characteristic of functional dis- 
orders is their susceptibility to various fantastic methods 
of treatment. In general, nearly any conceivable procedure 
or technique may cure such symptoms, provided the patient 
is convinced of its efficacy. The success of many systems of 

1 For a vivid analysis of the method whereby such disorders might be built up 
through learning, cf. Watson (26). 


mental therapy which have achieved widespread publicity 
can be attributed to this peculiar characteristic of func- 
tional symptoms. Similarly, the sudden, startling, and 
miraculous " cures" effected at various shrines, one of the 
best known of which is that of Sainte Anne de Beaupre in 
Canada, testify to the functional nature of the disorders. 
Dramatic incidents are recounted of the blind who sud- 
denly regained their vision, or of the crippled who aban- 
doned their crutches and walked forth erect. The same 
results have occasionally been observed in a severe emer- 
gency, as when a supposedly hopeless cripple arises from 
his chair to save a loved one from drowning or fire. 

The history of such cases usually reveals a certain ob- 
scurity of diagnosis. Physicians were baffled, the case was 
declared hopeless or a mystery, thus adding to the glamor 
of the "cure." What this suggests, however, is the func- 
tional nature of the disorder which naturally defied or- 
ganic diagnosis and treatment. 

In closing this brief survey, mention should be made of 
the fact that these disorders are no less "real" because 
they are functional. The subject may suffer just as acutely 
and be as seriously handicapped as if he had a definite 
structural deficiency. Similarly, such disturbances can- 
not be overcome merely by voluntary effort. Nor should 
they be confused with malingering. The subject himself 
is undergoing as vivid an experience as if he had an organic 
disorder and he may be completely unaware of the fact 
that his symptoms have no structural basis. 


Neuroses may be regarded as milder forms of personal- 
ity disorder than the psychoses. They are also more gen- 
erally regarded as functional in their nature than the 
latter. In their specific manifestations, they bridge the 



gap between the slightly maladjusted and emotionally 
unstable individual on the one hand and the distinctly 
insane on the other. On the basis of the normal distribu- 
tion of behavioral traits, we should expect neurotics to be 
more numerous than psychotics, since they are nearer the 
center of the curve. This seems to be borne out by obser- 
vation, although it is difficult to obtain accurate data on 
the relative incidence of such disorders because of loose 
methods of diagnosis. 

A common classification of neuroses recognizes three 
major types differentiated on the basis of symptomatology, 
wz., psychasthenia, neurasthenia, and hysteria. Typical 
psychasthenic symptoms are phobias, or abnormal fears, 
compulsions, obsessions, worries, restlessness, and irrita- 
bility. Neurasthenia is characterized by such symptoms as 
dizzy spells, headaches, excessive feelings of fatigue, di- 
gestive disturbances, and the like. Hysteria covers motor 
and sensory disturbances, such as tremors, contractions, 
paralyses, loss of sensation, and heightened sensitivity, as 
as well as fits of unconsciousness, loss of memory, and 
similar somnambulistic disorders. It has been suggested 
(cf. 14, pp. 403-404) that psychasthenia represents a dis- 
order on the intellectual, or symbolic, level, neurasthenia 
on the autonomic, or visceral, and hysteria on the postural. 

Neuroses, like psychoses, bear little relation to intellec- 
tual level. Neurotic symptoms occur over a wide range of 
mentality. In Table XV will be found the mental ages of 
.1172 soldiers in the United States army during the World 
War who manifested various neurotic disorders* These 
mental ages were determined by a variety of ways, in- 
cluding Stanford-Binet, performance scales, Army Alpha, 
a series of five specially selected tests, 1 or a combination 
of more than one of these methods. 

1 Completion, opposites, substitution, word-building, and digit span. 




(After Hollingworth, 13, p. 87) 








nosed \ 






























































































J 3 
















Over 1 8 
















* Not classifiable into a specific sub-form. 

f Undiagnosed at the time of testing, but believed to be chiefly neurotic. 

It will be noted that all of the disorders occur over the 
entire range of intelligence test scores, except psychas- 
thenia, which seems to be absent below a mental age of 
ten years. Thej^rious neurotic groups tend, however, to 

*f5 scale. It has been sug- 

gested on t:his.,tesis that intellectual ^ 

certain extent the p |^^ of neurotic symptom which an 
individual' will develop. Thus duller subjects are expected 
to "Be more susceptible to disorders of the hysteric type 
and brighter subjects to psychasthenia; neurasthenia 
occupies an intermediate position. The army data given 


in Table XV yield the following median mental ages for 
these three groups. 

Diagnosis Nu bes / ****** 

Cases M.A. 

Hysteria 177 11.5 

Neurasthenia 83 13.0 

Psychasthenia 1 10 14.0 

In evaluating these group tendencies, one must not lose 
sight of the fact that there is much overlapping between 
the groups and wide variation of intellectual level within 
each type of neurosis. The group differences themselves 
may be variously interpreted. Environmental factors, 
for example, might prove adequate to account for the 
slight relationship found between intelligence and nature 
of neurotic symptom. Individuals of lower intellectual 
status usually come from inferior social, economic, and 
educational levels. The problems and difficulties which 
they encounter are thus of a different nature from those 
which confront individuals in a superior environment. 
The emotional disorders developed by such groups can 
reasonably be expected to differ accordingly. 

One further point deserves mention in connection with 
the neuroses. One often hears the statement that neuroses 
are a product of the strain and stress of civilized life. 
The evidence cited is the appalling number of persons, 
now classed as neurotics, who visit psychiatrists or spend 
brief periods "recuperating" in sanatoriums. History, 
it is pointed out, bears little testimony to the presence 
of this class of individuals in former eras. The fallacy 
inherent in this argument is a common one. With the 
rapid development of psychology and psychiatry, there 
has come a more general recognition of neurotic conditions. 

1 It is of course difficult to generalize from only 10 cases, but data of other 
investigators agree in showing psychasthenics to have higher intelligence test 
scores than other neurotics. 


These mild abnormalities may have always existed, but 
they passed undiagnosed until the present. The neurotic 
is not sufficiently maladjusted in most cases to attract 
much attention or demand urgent treatment. In the 
past, such individuals may have gone their unhappy way, 
probably unpopular or disliked among their fellow-beings, 
but bearing their difficulties unlabeled and unrecorded. 
Similarly, the more highly developed the methods of 
diagnosis, the milder will be the disorders which are 
detected and the more numerous the individuals classified 
as neurotic. 


Recent interest in the study of abnormal conditions in 
widely varying cultural milieux hasjrevealedjJ^^ 
abnormality; is culturally defined. 1 There are two distinct 
ways in which specific cultural standards determine what 
shall be considered abnormal. First, the norm will differ 
from one group to another, so that any one specific be- 
havioral manifestation may occupy entirely different posi- 
tions in different distribution curves. An example from 
physical traits will make this clear. If we ask whether a 
given individual is "tall" or "short," we may obtain 
very different answers when different groups are employed 
as a standard. The same individual might be abnormally 
tall when evaluated in reference to the distribution of 
Japanese subjects, and abnormally short in terms of 
the distribution of Scandinavians. Similarly, in certain 
groups violent displays of emotions are the rule and 
stolidity would be abnormal. In others, the reverse is 

Secondly,. . cultui#]Jy,. M est^ 
which end of f the, .distribution -cwr ^^fAd^'^uto^z^^J"^^/'-- 

1 For a comprehensive and systematic analysis of this problem, cf. Foley (il). 


normal and which end subnormal. As has already been 
pointed out, such a criterion is intrinsically cultural in 
its nature. Comparative anthropology furnishes many 
instances of behavioral deviations which are regarded as 
unadaptive, pathological, insane, or mentally deficient 
in one culture and are admired or revered in another. 
Such behavior may be abnormal in both cases, in the 
statistical sense, but its social evaluation and practical 
value in the different cultures place it at opposite ends 
of the scale. This point has been clearly expressed by 
Benedict (i) who states: 

... it is probable that about the same range of individual 
temperaments are found in any group, but the group has 
already made its cultural choice of those human endowments 
and peculiarities it will put to use . . . the misfit is the 
person whose disposition is not capitalized by his culture. . . . 
It is clear that there is not possible any generalized descrip- 
tion of "the" deviant he is the representative of that arc of 
human capacities that is not capitalized in his culture (p. 24). 

The same point of view is further elaborated in a later 
article (2) by Benedict, in which appear the following 
statements : 

One of these problems relates to the customary normal- 
abnormal categories and our conclusions regarding them. In 
how far are such categories culturally determined, or in how 
far can we with assurance regard them as absolute? In how 
far can we regard inability to function socially as diagnostic 
of abnormality, or in how far is it necessary to regard this 
as a function of the culture? 

As a matter of fact, one of the most striking facts that 
emerge from a study of widely varying cultures is the ease 
with which our abnormals function in other cultures. It 
does not matter what kind of "abnormality" we choose for 
illustration, those which indicate extreme instability, or those 


which are more in the nature of character traits like sadism 
or delusions of grandeur or of persecution, there are well 
described cultures in which these abnormals function at ease 
and with honor, and apparently without danger or difficulty 
to the society (p. 60). 

As an example of behavior regarded as subnormal in 
our society, but valued and respected in other cultures, 
may be mentioned the conventional behavior of the Si- 
berian shaman, or priest (cf. 7). Such phenomena as 
cataleptic seizures often constitute an essential component 
of the behavior of the shaman. Similarly, trances, ex- 
treme introversion bordering on dementia praecox, manic- 
depressive behavior, and homosexuality are fostered and 
considered the ideal norm of behavior in various cul- 
tures. Paranoia, with its delusions of grandeur and its 
extreme suspiciousness, may be identified in the behavior 
and traditional chants of many medicine men or tribal 
priests. Illustrations could easily be multiplied from a 
survey of the behavior of different peoples. 1 - 


It should also be noted that behavioral deviations suf- 
ficiently pronounced to be classified as abnormal in the 
statistical sense are not an exclusively human phenome- 
non. Marked deviates can be found in all species. Mental 
deficiency, as well as "unadaptive" behavior which may 
be characterized as psychotic or neurotic, has been ob- 
served in many animal forms. Abnormal reactions rang- 
ing from drowsiness and sleep to overexcitability and 
violent emotional displays have been observed in chim- 
panzees when the latter were confronted with an " over- 
exacting" situation (cf. 3, Ch. VIII). Similarly, Pavlov 
(21) observed distinctly neurotic behavior in dogs in the 

1 Cf. Benedict (i, 2) and Foley (n). 


course of conditioning experiments. Symptoms not un- 
like those of the human "nervous breakdown" appeared 
when the animal was required to make too fine a sensory 
discrimination, or to set up too many conditioned reac- 
tions within a short time, or to establish a conditioned 
reaction when the two stimuli were separated by too long 
an interval. 

Homosexuality has been observed or experimentally 
induced among doves, pigeons, guinea pigs, white rats, 
and monkeys (cf. 12, 15). Several investigators (cf., 
e.g., 10, 12, 24) have reported instances of other types of 
abnormal behavior among monkeys, such as habit residu- 
als, temper tantrums, infantile reversions, and various 
forms of sexual perversions. These constitute abnormal- 
ities in the sense that they differ conspicuously from the 
usual behavior of the given species. Whenever the etiology 
of such abnormal behavior could be definitely traced, 
experiential or environmental factors were again found 
to play a predominant part (cf. 10, 12, 15, 24). 


We may now collate the diverse facts of abnormal be- 
havior reported in the preceding sections and attempt to 
characterize the nature of abnormality. First^ jJiere is 
nothing absolute about abnormality. The deviations 

, ^.jK.a^w^'^f'' v ^^ 

termed '" abnormal are relative and continuous. There is 
no sharp or clear dividing line between the normal and 
the abnormal, nor do abnormal symptoms differ qualita- 
tively from normal behavior. Such symptoms u are .only 

exaggeratiqjais, pi^Q^jmli^b^iorr'*^*"' *"**" 

Secondly, abnormality is specific (cf. n). Thejndj- 
viduaf may'T^ trait and yet Remain 

^^ft.^JL***. u**&M~+j a #il t &#>. Vt!llJ . - , ,' ,,. iM tftil^'iW*wM'<Sfc- i .&V*tAt*rt?#*2**'** 

u*M~+j a #il t &#>. Vt!llJ . - , ,' ,,. iM tftil^'iW*w'<- .* 

Thls 1S true of 
both intellectual and emotional traits and follows from 


the organization of behavior traits within the individual 
(cf. Chs. X and XI). 

Thirdly, psychological abnormality is to be defined in 
terms of Bebayior. In some cases, behavioral disorders 
may have structural concomitants, such as physical dis- 
eases, lesions, and malformations. But in the majority 
of cases no such physical basis can be discovered and it 
would only obscure the issue to attribute such behavioral 
manifestations to unknown organic causes. Analysis of 
the behavioral history and environmental stimulation of 
the individual, on the other hand, often reveals an ade- 
quate background for the development of the particular 
symptoms. Functional abnormalities are the special do- 
main of the psychologist and should be studied directly, 
without vague, hypothetical reference to physical con- 

Fourthly, abnormal behavior involves the same psy- 
chological principles as normal behavior. Abnormality 
i$ the normal result of certain stimulatin^Qflditions . Such 
behavior is termed abnormal only because it conflicts 
with the needs or standards imposed by a given culture. 
This is illustrated by two facts of cultural anthropology, 
viz., the shifting norm and the cultural evaluation of the 
direction of deviation. 


1. Benedict, R. "Configurations of Culture in North Amer- 
ica," Amer. Anthr., 1932, N.S. 34, 1-27. 

2. . "Anthropology and the Abnormal," /. Gen. PsychoL, 

1934, 10, 59-82. 

3. Bentley, I. M. The Problem of Mental Disorder. N. Y.: 
McGraw-Hill, 1934. Pp. 388. 

4. Binet, A., and Simon, Th. The Intelligence of the Feeble- 
minded (transl. by Kite, E. S.). Vineland, N. J.: Training 
School Publ. No. n, 1916. Pp.336. 


5. "British Royal Commission on the Care and Control of the 
Feebleminded," Report of the Commission. London: Wy- 
man, 1908. 

6. Burt, C. Mental and Scholastic Tests. London: King, 1921. 

7. Czaplicka, M. A. Aboriginal Siberia: a Study in Social 
Anthropology. Oxford: Clarendon Press, 1914. Pp.334. 

8. Doll, E. A. Anthropometry as an Aid to Mental Diagnosis. 
Vineland, N. J.: Training School Publ. No. 8, 1916. Pp. 91. 

9. Farrar, C. B. "Some Origins in Psychiatry," Amer. J. 
Insanity, 1907-08, 64, 523-552; 1908-09, 65, 83-101; 1909- 
10, 66, 277-294. 

10. Foley, J. P., Jr. "Second Year Development of a Rhesus 
Monkey (Macaca mulatto) Reared in Isolation during the 
First Eighteen Months," /. Genet. PsychoL, 1935, 47, 73-97. 

11. . "The Criterion of Abnormality," /. Abn. and Soc. 

Psychol, 1935, 30, 279-291. 

12. Hamilton, G. V. An Introduction to Objective Psychopathol- 
ogy. St. Louis: Mosby, 1925. Pp. 354. 

13. Hollingworth, H. L. The Psychology of Functional Neuroses. 
N. Y.: Appleton, 1920. Pp. 259. 

14. . Abnormal Psychology: Its Concepts and Theories. 

N. Y.: Ronald Press, 1930. Pp. 590. 

15. Jenkins, M. "The Effect of Segregation on the Sex Behavior 
of the White Rat as Measured by the Obstruction Method," 
Genet. PsychoL Mon., 1928, 3, 457-571. 

1 6. Klineberg, 0. Race Differences. N. Y.: Harper, 1935. Pp. 


17. Kraepelin, E, Clinical Psychiatry: a Textbook for Students 
and Physicians (abstr. and adapt, from Ger. ed. by A. R. 
Diefendorf). N. Y.: Macmillan, 1918. Pp.562. 

1 8. Morgan, J. J. B. The Psychology of Abnormal People. 
N. Y.: Longmans, Green, 1932. Pp. 627. 

19. Moss, F. A,, and Hunt, T. Foundations of Abnormal Psy- 
chology. N. Y.: Prentice-Hall, 1932. Pp. 548. 

20. Norsworthy, N. "The Psychology of Mentally Deficient 
Children," Arch. PsychoL, No. I, 1906. Pp. ill. 


21. Pavlov, I. Conditioned Reflexes: an Investigation of the 
Physiological Activity of the Cerebral Cortex (transl. and ed. 
by G. V. Anrep). Oxford Univ, Press: Humphrey Milford, 
1927. Pp. 430. 

22. Pintner, R. " The Feebleminded Child." Ch. 20 in Handbook 
of Child Psychology. C. Murchison, ed. Worcester, Mass.: 
Clark Univ. Press, 1933. Pp. 956. 

23. Terman, L. M. The Measurement of Intelligence. N. Y.: 
Houghton Mifflin, 1916. Pp. 362. 

24. Tinklepaugh, O. L. "The Self-Mutilation of a Male Ma- 
cacus rhesus Monkey," /. Mammal. ^ 1928, 9, 293-300. 

25. Tredgold, A. F. Mental Deficiency. N. Y.: Wood, 1922. 
Pp. 569- 

26. Watson, J. B. "Behavior and the Concept of Mental Dis- 
sease," /. Phil., PsychoL, and Sci. Method, 1916, 13, 


The existence of genius has probably been recognized 
by man from earliest times. In order to be popularly 
acclaimed as a genius, however, an individual must possess 
very exceptional talents of the kind demanded by his 
culture. Since only the extreme deviates attract notice, 
they seem by the very rare quality of their attainments 
to stand off from the rest of mankind and constitute a 
distinct group. With the advent of more objective meth- 
ods of observation and the development of testing 
techniques, the presence of lesser deviates who bridge 
the gap between the average man and the person of rare 
gifts has been demonstrated. Thus the popular belief in 
genius as a separate species arose in the same fashion as 
the similar belief regarding the feebleminded and it is 
being dispelled by the same methods. 

The relationship between genius and eminence is a 
curious one. Many writers identify the two by the simple 
expedient of defining genius as the possession of "what it 
takes" to become eminent in our society. The eminent 
man is then considered a genius ipso facto* There would 
thus be as many-kinds of genius as there are ways of -suc- 
ceeding in the particular society. The successful financier, 
for example, may be awarded an honorary university 
degree for his- "financial genius," the victorious- general 
for his "military genius."- Society often- creates a -new 
form of "genius" in order to rationalize its allotment of 

Almost any theory regarding the nature of genius could, 



of course, be defended by restricting the term genius in 
some arbitrary way. The broadest and most objective 
definition of genius is that of an individual who excels 
markedly the average performance in any field. Social 
evaluation, however, invariably enters into the concept. 
Genius is defined in terms of specific social criteria and a 
cultural sense of values. In our society the more abstract 
and linguistic abilities are considered the "higher" mental 
processes. Similarly, certain lines of achievement enable 
the individual to earn the appellation of genius much 
more readily than others. Thus academic and scientific 
work, literature, music, and the plastic arts are rated 
higher than, let us say, roller skating or cooking. 

To be sure, very exceptional accomplishments in the 
latter fields might be recognized as genius, after a fashion. 
An internationally famed roller skate acrobat or a re- 
nowned chef-de-cuisine might be called a genius and 
ranked higher than a mediocre scientist or painter. But 
in the former instances, the attainments must be propor- 
tionately far greater than in the latter in order that the 
individual may be designated a genius. And even when 
the term genius is applied to such cases, one feels that it is 
done only by courtesy and that the word is implicitly 
enclosed in quotation marks. It is apparent, therefore, 
that In order to have practical meaning, any definition of 
genius must recognize the selection of significant talents 
which has been made within a given cultural group. 

A further question which has been vigorously debated 
is that_olj^faLK^^ Is the man of 

genius one who manifests a well-rounded intellectual 
superiority or one who possesses a highly specialized gift? 
It follows from the organization of mental traits that this 
distinction is not a valid one. Siqcs th& iuteicorifelatious 
of diverse abilities^ are ^nejtherJbigU 


should expect all degrees of generality of 
.genius. A .few individuals may excel highly in a large 
its _. and thus^apgear^to, y be all-around gen- 

ius^s. Some will excel in only a few, traits ? - and still others 
may haye ,a single talent which- is, sufficiently pronounced 
tQjpiLt.lhera in the category of, genius. There is no neces- 
sary relationship, either positive or negative, between 
excellence in one trait and in any other. 


Theories on the nature and causes of genius are legion, 
The genius has been credited with a wide variety of 
attributes, ranging from divine inspiration and a super- 
human "spark" to imbecility and insanity. Among these 
diverse theories it is possible to discern four underlying 
viewpoints. These will be designated the pathological, 
psychoanalytic, typological, and deviationaL 1 

Pathological tjieoriesj^ 

.degeneracy! and even feeblemindedness. This view was 

*SW3F*<^^ *" '" " ' " " """'!.' -"i" 

put forth by many of the ancient writers, among whom 
may be mentioned Democritus and Seneca. More re- 
cently, it received clear expression in the writings of 
claimed that all genius is a neurosis, and 


out, is equally cha^tejj^ji^^ 

EssenHallythe same theory was later expanded by Nisbet 
(24) in England, who held genius to be a mere sport of 
nature or spontaneous variation which betrays a lack of 
adaptation to its environment. 

The greatest impetus to the development of the patho- 
logical view* 4 of^f Sinus "was probably furnished by the 

1 These terms are only employed as convenient designations and are not to be 
regarded as a sufficient characterization of any of the views. The terms "typo- 
logical" and "deviational," for example, should be accompanied by qualifying 
adjectives, but the latter are omitted for the sake of conciseness. 


Italian anthropologist, Lombroso (22). His book entitled 
The 'Man of Genius was translated into several languages 
and read widely at the turn of the present century. In it 
he attributed to the genius a wide variety of qualifies 
which he regarded as indicative of species degenerajipn. 
Among them are included short stature, rickets, excessive 
pallor, emaciation, stammering, left-handedness, delayed 
development, and originality! He also claimed to have 
observed a certain similarity between the creative act of 
genius and the typical epileptic seizure. 

Havelpck Ellis (12) proposed a, two-fold, theory which 
Ttc^iiZQ^^c^ceptional talents of genius but ^at the 
same time includes a certain essential deficiencyjin the 
complete picture. This deficiency he regards as some in- 
nate organic inaptitude which prevents complete adjust- 
ment to the activities of everyday life. He cites as exam- 
ples motor incoordination, narrow specialization with 
attendant inferiority in other fields, impracticality, and 
similar deficiencies occasionally found in men of genius. 1 

The evidence presented in support of these views con- 
sists of illustrative examples of geniuses who manifested 
the alleged traits. Such evidence is open to all the criti- 
cisms of selected cases. A few individuals can be found to 
illustrate almost any theory. Only the objective observa- 
tion of large numbers of unselected cases can furnish an 
adequate test of these assumptions. This type of evidence 
will be presented in a subsequent section. 

Several factors can be cited which might erroneously 
suggest a linkage between insanity and genius. Thus 
many geniuses of high degree may become maladjusted 
In a society built up around the average man and his 

1 This theory might also be classified under the psychoanalytic viewpoints, 
owing to a certain resemblance to the Adlerian concept of organic inferiority in 
genius (cf. below). 


needs. This is particularly noticeable in the case of a 
very superior child placed in a class of mediocre school- 
children. It is equally true of superior adults. Geniuses, 
furthermore, are often regarded as pathological by their 
fellow-men until the practical benefits of their work be- 
come tangible. Their achievements are ridiculed until 
they succeed. The familiar example of Fulton and his 
steamboat is a case in point. Occasionally, the genius 
has met with systematic and even violent opposition 
from the church or other organized bodies. Life under 
such conditions was not very conducive to the develop- 
ment of a stable and well-adjusted personality. Finally, 
it may be added that even when the genius is recognized 
and acclaimed as such, he is likely to be surrounded by 
such a blare of publicity that all his actions and idiosyn- 
cracies become common knowledge. As a result, any 
behavioral deviation too slight to attract attention in a 
less outstanding individual is pounced upon, discussed, 
and elaborated until it may assume the proportions of a 
neurotic or psychotic symptom. 

of .genius emphasise .motiva- 

tion^^ intellectual characteristics. The psy- 

choanalytic concepts o^^^sublimation and compensation 
are brougj^j^j^acoount foT^e^rcmSlaQe, achievements 
ofgenius. Freud (cf. 10) regards the manifestations of 
genius as a sublimation or substitute outlet for a thwarted 
sex drive. He does, however, recognize the need for a 
certain degree of talent together with strong motivational 
factors. Adler (i) regards the exceptional accomplish- 
ments of genius as compensations for other inferiorities, 
usually of an organic nature. A favorite example is that 
of great orators, such as Demosthenes, who developed 
their talent by overcompensating for an initial habit of 
stammering or some similar speech defect. 


The role of motivational factors in the development of 
genius cannot be ignored. Under certain conditions, a 
slight physical handicap may spur the individual on to 
greater efforts and thereby contribute indirectly to his 
success. Similarly, thwarted desires or emotional dis- 
appointments may cause some individuals to turn to 
intellectual pursuits as a consolation. Restriction of one's 
range of activities by physical defects, unpopularity, or 
other conditions may also lead to more intensive work 
and subsequent success along a particular line. These 
various motivational influences are very simple and clearly 
observable facts. The psychoanalytic theories, on the 
other hand, are burdened with vague concepts, fantastical 
allusions to Unconscious forces, and mystifying state- 
ments. The simple issues involved are greatly confused 
by such interpretations. These theories, furthermore, 
could only account for a relatively small number of gen- 
iuses. Nor do they offer a satisfactory interpretation of 
the essential nature of genius. 

Those views which we have classified under the heading 
of typological r^ard ww g^ius asja distinct type differing 
cfSsX^^S^imm the i>( rest w ^ Such views 

are to be distinguished from the pathological and the 
psychoanalytic in that they regard the man of genius as 
essentially superior to the norm. No inferiorities of any 
sort are implicit in this concept. The achievements of 
genius, according to these theories, result from some 
process or condition which is entirely absent in the ordi- 
nary man. Such current expressions as "the spark of 
genius " reflect the popular influence of this point of view. 

The typological approach, like the pathological, has a 
long history. 1 In the ancient world, genius was frequently 
attributed to divine inspiration. The Greeks spoke of a 

1 Cf. 17 and 29 for references. 


man's "daemon" which was supposed to possess divine 
powers and to furnish the inspiration for his creative 
work. Among those who discussed genius In these terms 
may be mentioned Plato and Socrates. Christianity ad- 
vanced the view that genius was the inspiration of a 
selected mortal by God. Or, in some cases, it was Satan 
who provided the creative talents, especially when the 
inspiration was of a kind contrary to the dogmas of the 

Qualitative distinctions are also common in literary 
and philosophical writings on the subject of genius. Mys- 
tic insights and unconscious intuitions have been at- 
tributed to the man of genius. In this connection may 
be mentioned the views of Schopenhauer, Carlisle, and 

In psychological discussions of genius, this point of 
view is much less common. r G. Stanley Hall's proposal 
(16, p. 320) ^^.th^sh^^^^^^'^'S^^ are. similar 
to those of , tjae, jidqiescent may be regarded as a qualita- 
tive :' distinction. Recently Hirsch (17) has put forth a 
distinctly qualitative view. He attempts to differentiate 
three "dimensions" of intelligence. The first dimension 
is perceptual and cognitive and is shared by man and the 
lower animals; the second is conceptual and is common 
to all of mankind; the third he designates "creative 
intelligence" and attributes only to genius. 

Qualitative distinctions appeal to the imagination of 
the public. The genius whom the layman acclaims differs 
so greatly from the rest of mankind in his achievements 
that he seems to belong to another species. A careful 
analysis of the individual's abilities, however, will reveal 
no essentially new process. And only a brief unbiased 
search discloses the presence of intermediate degrees of 
capacity in all lines. 


The deviational view regards genius only as the upper 
extreme of the normal distribution curve. The special 
"gifts" and " creative powers" of genius are possessed, 
to a much lesser degree,, by all individuals. Distinctions 
are quantitative and not qualitative. Genius is defined 
in terms of concrete, measurable behavior rather than in 
terms of mystical entities. To be sure, the accomplish- 
ments of genius are not attributed to any single talent, 
but to a favorable combination of several intellectual, 
motivational, and emotional factors. 

It follows from the deviational view that the origin of 
genius is to be understood in the same terms as that of all 
individual differences. Many writers on the subject of 
genius, such as Galton (13, 14), Terman (31, 32), Cox (8), 
L. S. Hollingworth (18), and Pintner (26, Ch. 15), lay 
the major emphasis upon hereditary factors. The ob- 
servation that genius runs in families has probably given 
the greatest impetus to this view. In such cases the po- 
tent environmental influence exercised by family tradi- 
tions and family contacts is overlooked. For an analysis 
of the operation of hereditary and environmental factors 
in the development of individual variations in general, 
the reader is referred to Chapters III, IV, and V. 


Psychological investigations on the nature and develop- 
ment of genius have followed a variety of procedures. 
These may be classified into: (i) biographical analysis, 
(2) case study, (3) statistical survey, (4) historiometry, 
and (5) mental measurement. In biographical studies, 
all available printed material on a given individual is 
examined in the effort to arrive at an understanding of 
the nature and origin of his genius. The investigation is 
limited to a single individual, who is usually chosen from 


the great men of the past. This method has been em- 
ployed chiefly by psychoanalysts, but it is also occasion- 
ally used by psychologists. 

The case study method consists of direct and controlled 
observations of a single living individual. Because of the 
difficulty of subjecting adult geniuses to such an investiga- 
tion, this method has been applied almost exclusively to 
gifted children. Several such studies on contemporary 
child prodigies, and especially juvenile authors, have been 
initiated by psychologists. 

The statistical survey method, like the biographical, is 
based upon an analysis of printed records. It differs 
from the latter method, however, in several essential 
respects. The purpose of statistical surveys of genius is 
to discover general trends in a large group, rather than to 
make an exhaustive analysis of a single case. All avail- 
able information on a large number of men is obtained 
from biographical directories, encyclopedias, Who's Who, 
and similar sources. This material is occasionally sup- 
plemented from biographies. But the former sources are 
employed predominantly because of the more objective, 
reliable, and standardized nature of their data. It will 
be noted that in this method the criterion of genius is 
chiefly eminence. 

The historiometry method makes use of all historical 
material on an individual or a group of individuals. The 
data are culled from a variety of sources, including bi- 
ographies, directories, and original documents such as 
letters and diaries. The attempt is made to obtain as 
complete information as possible, especially on the child- 
hood accomplishments of the great man. This material 
is then evaluated in terms of a more or less constant 
standard in order to arrive at an estimate of the indi- 
vidual's traits. This method was employed by Woods (34) 


in his study of mental and moral heredity in royalty. 
Terman (28) subsequently suggested an adaptation of 
historiometry whereby the recorded achievements are 
evaluated in terms of mental test standards and norms 
of performance for each age. From this, an estimate is 
obtained of the individual's I.Q. in childhood. Terman 
estimated by this method, for example, that the I.Q. 
of Francis Galton was approximately 200. 

The mental measurement method consists of the direct 
study of large groups of intellectually superior children 
by means of mental tests. Extensive use is now being 
made of this method. The subjects are originally selected 
on the basis of intelligence test performance, and subse- 
quent analyses are made with the aid of standardized 
intellectual, scholastic, and personality tests. 

Each of these procedures contributes something which 
is lacking in the others. Similarly, each by itself suffers 
from special weaknesses. The statistical survey, histori- 
ometry, and mental measurement methods can be applied 
to large groups, and hence disclose general trends. They 
are also relatively free from selectional bias. The bio- 
graphical and case study methods, on the other hand, 
give a more complete picture of the individual and enable 
one to note the specific action of various conditions upon 
the subject's development. The study of contemporary 
living geniuses makes direct observation possible and 
avoids the judgment errors and other inaccuracies which 
are inevitably present in historical material. On the 
other hand, carefully controlled observation on living 
geniuses offers many practical difficulties. A further dis- 
advantage in the study of contemporaries is the possibil- 
ity that the eminence of some may be short-lived and 
spurious and that others who are laboring in obscurity 
may be recognized as geniuses by posterity. 


Finally, the relative advantages of studying adult gen- 
iuses and gifted children may be considered. To investi- 
gate intellectually superior children in the effort to dis- 
cover the characteristics of adult geniuses seems somewhat 
indirect. Only a small number of such children, further- 
more,, will develop into adults who can be classified as 
geniuses. Children, however, are available for prolonged 
and controlled observation and testing which would be 
practically impossible with adults. A further advantage 
of the study of gifted children is that it offers a genetic 
approach to the problem. Such an analysis may go far 
towards clarifying the origin and nature of genius. 


Investigations on genius through statistical surveys of 
printed records have been conducted in England by Gal- 
ton 1 (13, 14) and Ellis (12), in France by de Candolle (9), 
Jacoby (21), and Odin (25), and in America by Cattell 
(4, 5, 6), Brimhall (2), and Clarke (7). Castle (3) con- 
ducted a similar survey on eminent women of all countries, 
but the data of this study are extremely tentative and 
quite difficult to interpret. The major findings of these 
studies will be summarized briefly. 

Zte^0g/^ has 

been generaUyJjjj^^ the 

entire" population. Thus in Cattell's analysis of the oc- 
cupations of the fathers of American men of science (5), 
the percentage engaged in the professions was far in 
excess of that in the general population. The relevant 
data are reproduced in the following table. C^S^^^mr 

- " Ws B3I co^clwc 
ofjoiuLon^qf .science ppme from 

1 Cf. Ch. IV for a discussion of specific procedure and results. 


Occupational Group 

Percentage in Each Occupational Group 

Fathers of American General Population 
Men of Science in 1850 l 

Manufacture and trade 





population most favorably situated to produce them % The 
son of a successful professional man is fifty limes^asjikely 
to become a leading scientific man as a boy .taken at 
random from the community" (5, p. 511). 

A similar distribution of occupational level is to be 
found among the eminent men and women surveyed by 
Ellis (12). In Castle's study (3) of eminent women of 
all times and nationalities, it was reported that 33.1% 
had fathers in the "learned professions." ^Cox (8, p. 37) 
obtained the following distribution of paternal pccupation 
in a group of 282 eminent men and women Qf.a^^ountries. 

Occupational Level Percentage 

1. Professional and nobilit7 S 2 -S 

2. Semi-professional, higher business, and gentry 28.7 

3. Skilled workmen and lower business 13 - 1 

4. Semi-skilled 3*9 

5. Unskilled i-i 
No record 0.7 

The number of eminent relatives is also of interest in 
this connection. It will be recalled that in ^alton's 
studjr (13)^ the ,97^eoune^ 
of 73 9 known rej^^ 

It_mll alsp , be recalled, thaty in. general,,, the, .ctasfiT the 
degree of relationship, ^the more numerous, ."weie^lhc^nii- 
ne$t relatives^ Similar results were obtained in Brim- 
hairs investigation (2) of family resemblance among 
American men of science. 

1 Corresponding roughly to the time when the fathers of the scientific men had 
pursued their vocations. 


Rather suggestive evidence for an environmental in- 
terpretation of the development of genius is furnished 
by Cattell's analysis of the place of birth of American men 
ofjaence (cf. 4, 6). In his 1906 report^ Cattell pointed 
out that cities contributed a much greater proportion of 
men of science than did rural sections. Although at that 
time the urban population was about one-sixth of the 
rural population, it produced a quarter of the scientific 
men. Even more striking is the comparison of different 
states which varied widely in their educational facilities. 
Below are shown the relative number of scientists born 
in each of nine states. The latter have been chosen as the 
clearest examples of a definite trend which has been 
operative during the last three decades. Corresponding 
figures are shown for the original group of 1000 scientists 
selected in the year 1903 and for the group of 250 elected 
in 1932. All figures have been expressed in terms of 
1000 entries to permit direct comparison (cf. 6, p. 1265). 

Number of Cases 

Place of Birth (in terms of 1000 entries) 

1903 1932 







New York 





















These dajtgjsuu^ 

m^SJ^everal conclusions which are 

Lit b-tJie,^QmDtete results^loTSI^^S^^SLfflMEtr; 

(cf. 6). lujAe fii^dafis. there are marked discrepancies 

^-~- ' "^^^^miMii^^ MAM*** . 



in birthplace correspond very closely to differences in 
educational opportunities in various sections of the coun- 
try. Thirdly, as educational facilities change,, the fre- 
quency of scientists shows a corresponding change. In 
recent years, for example, there has been a phenomenal 
development of education in the mid-western states. The 
relative quality of education in such states has improved, 
new universities have been established, the number of 
students in institutions of higher learning has increased 
rapidly, 1 and a powerful tradition has been built up which 
fosters intellectual activity. These factors probably ac- 
count for the definite rise in the number of scientists from 
mid-western states, as compared to the New England 
states which were formerly the undisputed center of the 
intellectual life of the country. 

Of interest in connection with the pathplQglcal.,theories 
ofjsjemus Js the relative frequency of insanity among the 
relatiY,ei^Ql eminent .men, 43 wll, as .among .the .. siibj ects 
themselves. In all well controlled studies in which the 
cases were not selected to prove a point, the incidence of 
intellectual and emotional disorders has been found td* be 
consistently smaller among eminent men and their families 
thanjL^^ In the group investigated 

by Ellis "(12, p, 192)3 less than 2% were reported to have 
had either insane parents or insane offspring. Among the 
eminent individuals themselves, Ellis mentions 44 cases of 
emotional disorder out of a total group of 1030. Of these, 
only 13 could be definitely classed as insane during the ac- 
tive period of their lives; 19 were either insane for a short 
period or manifested very mild disorders; and 12 developed 
senile dementia in old age (cf. 12, pp. 189-190). 

1 Cf., e.g., Eells' analysis of the "center of population" of higher education 
from. 1790 to 1920, which showed a westward movement at the rate of 60 miles 
per decade (n). 


Other facts which have been brought to light by these 
surveys relate to age of pjzrents at, the., timt.Q/^birth of the 
child, order of birth, and similar "vital statistics. " It has 
been proposed, for example, that older parents have in- 
tellectually superior children (cf. 27). From a somewhat 
different angle, Lombroso (22) claimed that geniuses are 
the offspring of aged parents and offered this as further 
evidence of the pathological nature of genius. The data 
on this question are difficult to interpret because of the 
complicating factor of social level. People in the higher 
social classes, from which geniuses are most frequently 
recruited, tend to marry later and therefore have children 
at a later age. For this reason average ages are in them- 
selves inconclusive. Among American men of science, 
III) found 35 years to be the average agp of 
pi, A, sub j ect' ,& birth. For English 

men of science, Galton (14) found the corresponding 
figure to be 36 years. Ellis (12) gives 37.1 years for his 
group of British men and women of eminence. In all of 
these groups, however, the range of parental ages at birth 
is extremely wide. In the majority of cases the parents 
were in the prime of life at the time of the subject's birth, 
contrary to Lombroso' s contention. 

Somewhat more conclusive is the analysis of order of 
birthjw^^ the 'eminent individual 

is most oftenjJie oldest^r first-born child in the family. 
NeS^ comes the youngest child, 

intermediate children having tEeleast ^aiTS'orBecGmmg 
eminent (cf. 12, 35). These findings are in direct contra- 
diction to the proposed theory that older parents have 
intellectually more gifted offspring. It would seem that, 
within the same family, the superior child is most likely 
to be born when the parents are younger. This finding 
may be interpreted in cultural terms. The first born has 


traditionally enjoyed privileges in our society that his 
younger siblings may not have had. More is usually 
expected of the oldest son. If a choice must be made for 
economic reasons, the oldest child is usually allowed to 
complete his education, in preference to the younger 
children. These conditions might be sufficient to produce 
a slight degree of relationship between birth order and 


The childhood of great men, viewed retrospectively, 
has been the source of much controversial discussion. 
There is a popular, belief l that many geniuses ;were dulHn 
childEood. Several examples are cited in support of this 
contention. Darwin was considered by his teachers to 
be below average in intellect. Newton was at the bottom 
of his class. Heine was an academic failure, revolting 
against the traditional formalism of the schools of his 
time. Pasteur, Hume, von Humboldt, and other equally 
famous men were unsuccessful in their school work. 

An examination of the ay arable,, biographical material 

in sucE^Eai^ wasjn- 

fe"rre3 from scholastic, achievements of a rather narrow 

'scope. The intellectually superior child may be just as 

"maladjusted in school as the dull or borderline case. 

cMld may be mjsuited 

to tl^JiigM^^ The monotonous 

*3rill and rote memorization which constituted such a 
large part of school work in the days when men like Darwin 
or Hume attended school would prove particularly irk- 
some to a bright child. Darwin, for instance, seems to have 
been more interested in his collections of insects than in 
memorizing Latin declensions, much to the annoyance of 

1 Also proposed by Lombroso (22). 


his teachers. Thus it is often impossible to accept the 
recorded opinions of parents or teachers regarding the 
intellectual status of great men in childhood. 

More accurate information can be obtained from fac- 
tual records of the specific behavior of the individual at 
various ages. An early attempt to conduct such an analy- 
sis of the boyhood of great men was made by Yoder (35). 
Fifty cases, representing a wide variety of occupations or 
fields of eminence, were selected from the great men of 
six countries. All of the subjects were bora in the eight- 
eenth or nineteenth centuries, except Newton, Swift, and 
Voltaire, who were born in the seventeenth. In general 
Yoder found that ill health in childhood was often exag- 
gerated by the earlier biographers and that this condition 
was not so prevalent as is supposed. Feeble or delicate 
health may, however, offer advantages in some cases by 
stimulating reading and intellectual pursuits. Dickens 
was a good example of this. In regard to intellectual 
status, Yoder reports that excellent memory and vivid 
imagination were often exhibited by great men from 
early childhood. 

A very painsta^ the 

chgd^cf^jreat men WM ^Q^Ptpd,]?J n Cox (8). JEer- 
man r s aclajDtatipn pj^thejh^ 

pfoyiX " T hrougli the examination of several thousand 
biographical references, information was gathered on the 
traits of 301 eminent men and women born between 145 
and 1850. Particular attention was given to childhood 
behavior, such as age of learning to read, letters and 
original compositions which may have been preserved, 
early interests, etc. Any special 'circumstances which 
might have influenced the subject's development were 
also noted. The materia^^ and 



Each investigator estimated the lowest I.Q. compatible 
with the given facts for every subject, and the average of 
these three independent judgments was taken as the 
final minimum I.Q. estimate for the given individual. 

After allowing for certain inaccuracies in the data, Cox 
concludes that the average I.Q. for the group "is not 
below 155 and probably at least as high as 165" (8, p. 217). 
The estimated minimum I.Q.'s ranged approximately from 
100 to 200. The same geniuses cited by Lombroso and 
others as instances of early mental inferiority were in- 
variably found to give evidence of high I.Q.'s during 
childhood. Among these may be mentioned Lord Byron, 
Sir Walter Scott, and Charles Darwin, whose estimated 
I.Q.'s proved to be 150, 150, and 135, respectively. Among 
those receiving I.Q.'s above 180 were Goethe, John Stuart 
Mill, Macaulay, Pascal, Leibnitz, and Grotius. 

In addition to intellectual superiority, Cox emphasizes 
the^tmpoftance of favorable" personality traits in tjie 
development of genius. Among such traits she mentions 
"persistence of motive ancT effort, confidence in their 
aHHities, and great strength or force of character" (8, 
p. '218). Em^nt^jelatives ? superior home background, 
anyd_opggrtumlies, for education ami intellectual contacts 

Thus it seems that genius is usually foreshadowed by 
the intellectual and temperamental traits of childhood. 
The geniuses of tomorrow are probably to be found 
among the gifted children of today. This, coasisteacy of 

SUQSQQC iftGCQJWJis^^ id- 

eation of the hereditary determination of genius. It might, 
on Jijie^ pth^baad^ ., -be, regarded simply,, as illus f ti:aJ;TO^of 
the major irapQrtaixce, of e$rly tnvimnjney>t* The nature 
and direction of the individual's subsequent abilities are 
largely determined by the circumstances of his early life. 


It may be for this reason that the achievements of the 
adult are reflected in the interests and proclivities of his 


Since geniuses have generally displayed superior talents 
in childhood, a direct study of gifted children should 
prove relevant. The traditional or popular concept of 
the "child prodigy" is that of a weak, sickly, unsocial, 
and narrowly specialized individual. His achievements 
are expected to be of the nature of intellectual "stunts" 
and to have little or no practical value. 

One of the earliest recorded cases of such a child prodigy 
is that of Christian Heinrich Heineken, whose achieve- 
ments are described by his teacher in an old German book 
published in 1779 (cf. 26, pp. 352-353). At the age of 
10 months this child was able to name objects in pictures. 
Before the age of 12 months he had memorized many 
stories in the book of Moses. At 14 months he knew the 
stories of the Old and New Testaments. At 4 years of 
age he could read in his native language, had memorized 
1500 sayings in Latin, and also knew French. At this 
time he was able to perform the four fundamental arith- 
metic operations, and he knew the most important facts 
of geography. His fame spread throughout Europe and 
he was summoned to appear before the King of Denmark. 
True to the traditional picture, however, Christian Hein- 
rich was a sickly child, and at the age of 4 years-4 months 
he died. 

Contrary to popular belief, the case of Christian Hein- 
rich is not typical. As an example of a highly gifted child 

1 A discussion of teaching methods suitable for gifted children is beyond the 
scope of this volume. For a number of studies on this problem the reader is 
referred to the Twenty-third Yearbook of the National Society for the Study of 
Education (36). 


who developed into a healthy and successful adult may 
be mentioned Karl Witte (cf. 33). Born in Lochau, 
Prussia, in 1800, this " child prodigy" lived until he was 
83, having retained his excellent intellectual powers to 
the end. Karl was literally educated from the cradle. 
His father was convinced of the efficacy of early training 
and undertook to prove this with his son. The child was 
never taught "baby talk." All the games he played were 
games of knowledge. When only 8 years old, he read with 
apparent pleasure the original texts of Homer, Plutarch, 
Virgil, Cicero, Fenelon, Florian, Metastasio, and Schiller. 
He matriculated as a regular student at Leipzig at the 
age of 9. Before his fourteenth birthday he was granted 
a Ph.D. Two years later he was made a Doctor of Laws, 
being at the same time appointed to the teaching staff 
of the University of Berlin. 

Karl Witte's father, in discussing the boy's education, 
wrote : 

... he was first of all to be a strong, active, and happy 
young man, and in this, as everybody knows, I have suc- 
ceeded. ... It would have been in the highest degree un- 
pleasant for me to have made of him preeminently a Latin 
or a Greek scholar or a mathematician. For this reason, I 
immediately interfered whenever I thought that this or that 
language or science attracted his attention at too early a 
time (33, pp. 63-64). 

Karl seems not to have been in the least vain or spoiled. 
He never paraded his knowledge, was modest and un- 
pretentious, and not infrequently tried to learn from his 
companions what they knew better than he. He had 
many playmates of his own age and we are told that: 
"He got along so well with them that they invariably 
became very fond of him and nearly always parted from 
him with tears in their eyes" (33, p. 187). 


Recent case studies of gifted children by psychologists 
likewise lend no support to the view that such children 
are inferior in other respects. The gifted "juvenile 
author/' Betty Ford, obtained a Stanford-Binet LQ. of 
1 88 when tested at the age of 7 years-io months (cf. 30). 
She ranked high in all other intellectual and educational 
tests, but showed a special interest and talent for the 
composition of prose and poetry. This child was reported 
to be in excellent health and free from physical defects. 
She was found to be a year or so accelerated in physical 

Betty Ford's superior linguistic abilities were apparent 
from an early age. At 19 months she could express her- 
self clearly and also knew the alphabet. By her eighth 
birthday she had read approximately 700 books, includ- 
ing such authors as Burns, Shakespeare, Longfellow, 
Wordsworth, Scott, and Poe. By this age she had also 
written over 100 poems and 75 stories. The following is a 
specimen of her literary products, written at the age of 
7 years-n months and entitled "Fairy Definition": 

Fairies are the fancies of an imaginative brain 
Which wearying of earthly realities aspires to 
Create beings living only in thought 
Endowing the spirits thus created 
With all genius for giving Happiness. 

A case which attracted wide attention a few years ago 
is that of a boy known in the psychological literature as 

E . When first tested at the age of 8 years~u months, 

E obtained a mental age of 1 5-7, which gave him an 

LQ. of 187. He also did well on all other tests except 
those involving manual dexterity. He is reported as 
being strong and healthy, but not much inclined to in- 
dulge in games and sports. At the age of 12 he was ad- 


mitted to Columbia College. On the Thorndike Intelli- 
gence Examination for High School Graduates, he ranked 
second among 483 competitors. During his freshman year 
at college all his academic grades were B or better, with 
the exception of physical education, in which his grade 
was C. He is described as being a "good sport" and 
getting along well with the other students. He received 
his A.B. degree at 15, being also admitted to Phi Beta 
Kappa. At 16 he obtained his M.A. degree, and at 18, 
when the final report appeared, he was well advanced 
towards the Ph.D. degree. On the CAVD Intelligence 
Examination, his score was 441, which falls approximately 
in the upper } of i% of college graduates. Thus during 

the ten-year period over which he was investigated, E 

showed no tendency to drop below the high intellectual 
level indicated by his initial LQ. 

These cases are typical examples of intellectually superior 
children. Exceptional talents in childhood 4,re not incom- 
patible with good health, physical vigor, longevity, or a well- 
rounded personality. To be sure, puny, timid, and sickly 
"children can be found among the gifted, as among the intel- 
lectually normal or dull. But such cases are very few and 
cannot be regarded as representative of the group as a whole. 


Mental test surveys of large groups of intellectually 
superior children have revealed the continuity which 
exists between the average child and the highly gifted 
"prodigy. " In order to include a sufficiently large number 
of cases in such studies, the standard of selection must be 
lowered. But by surveying a wider range of superior 
intellect, a more complete picture will be obtained. Since 
the rise of the mental testing movement, a number of 
studies on moderately large groups of superior children 


have appeared (cf. 29 for references). The most extensive 
investigations so far conducted by the mental test 
method are those of Terman and his associates, reported 
in Volume I of the Genetic Studies oj Genius (31). Because 
of the more comprehensive nature of this study and its 
essential agreement with the findings of other investiga- 
tions, it will be described in greater detail. 

The major group employed in Terman's study consisted 
of 643 California schoolchildren between the ages of 
2 -t an3Ti4, whos^Stanford-Binet LQ.'s were 140 or above. 
3Tlpecial study was also conducted on 378 high school 
students. In the main study, the gifted children were 
compared in each of a series of tests or measures with 
equated control groups of intellectually normal children. 
For reasons of expediency, different control groups were 
employed for various comparisons, the number of cases 
in such groups ranging from about 600 to 800. 

The social and cultural level of the gifted group was 
In regard to paternal occupation, 31.4% 

belonged to the professional class, 50% to the semi- 
professional or higher business class, n.8% to the skilled 
labor class, and less than 7% to the semi-skilled or un- 
skilled labor class. The average cultural rating of the 
home l was 22.94 as compared to 20.78 for unselected 
homes. The, ayer3g<^ school .grade reached by the parents 
of the gifted group was 11.8 and by the grandparents 
foro. * These figures may be compared with the average 
ainount of schooling of the native-born White draft of 
the United States army in the World War, which did not 
quite reach the seventh grade. It should be noted that 
the average age of the army draft was about 15 years 
lower than that of the parents of the gifted children and 

1 Obtained by the Whittier Scale, which takes into account necessities, neat- 
ness, size, parental condition, and parental supervision. 


much lower than that of the grandparents. Since the 
amount of schooling has risen markedly in recent years, 
the showing made by the parents and grandparents of 
the gifted group is even better than it appears. In addi- 
tion, over one-fourth of the children had at least one 
parent who was a college graduate. The number of emi- 
nent relatives and ancestors was also far in excess of that 
which would be expected through chance, and many of the 
families had highly distinguished geneplogies. 

We may next consider certain vital statistics as well as 
medical and anthropometric data obtained on the gifted 
arid" control groups. As in the studies on adult genius, a 
fc pEHpondenee -of -first-born: -chiid-rea.. -was found in the 
gifted group. The reque$cyx>f insanity in the family was 
'mucTi lower than average. Only 04% of the parents and 
0.3% of the grandparents and great-grandparents were 
reported to have had a record of insanity. The gifted 
children developed at a rapid rate from early infancy. 
They ^alked.oix.lhe.^v^X^ge ^qne^mpnth earlier and talked 
2| months earlier than -the, control groups. The onset of 
puberty was also somewhat earlier than normal. Physicians' 
examinations showed superior health and relative freedom 
from defects in the group as a whole. Similarly, such con- 
ditions as "nervousness," stuttering, headaches, general 
weakness, and poor nutrition were less common in the gifted 
than in the control groups. In ^ej^ht*and wdg^physical 
and muscular development, and, strength, the overlapping 
of "gifted "and contror^ro ups, ,wasu Almost , complete. Such 
differences as did occur, however, favored the gifted group. 


ih , 
were, of course, Jan ,i& . adyaace-of-4he- -normal. 1 About 

1 This was partly the result of the method of selection. Teachers were asked 
to name the brightest children in each class, and from among these the gifted 
subjects were chosen by mental tests. 


f ^e gifted children were accelerated and none were 
The administration of standardized achieve- 
ment tests in school subjects revealed, however, that the 
majority of these ^children had already mastered the 
sl iyLJSSir fronToae to three grades above that in 
which they were located. Thus in respect to actual 
abilities, tEe gifted child is often retarded and not acceler- 
ated in school status. The performance of the gifted 
children as a group was fairly uniform in different school 
subjects. One^idedness was not characteristic of the 
group- The superiority of the gifted children was, how- 
ever, greater in such subjects as language usage, reading, 

^BdJl3^H5S.! J .??!9^ anc * ^ east ' m manual training, paint- 
ing, and similar abilities. 

Thejgifted 8 rou P displayed a wide range of interests 
9S^^9l^?l^^P9^P r ^ as we ll as an active play life. 
A two-months reading record kept by the children showed 
that the gifted subjects read more than the control at 
all ages. At 9, the number of books read by the gifted 
group was three times that of the control. The range of 
topics covered was also wider and the quality of the 
books superior in the gifted group. Similarly, the gifted 
children were more enthusiastic, had more intense inter- 
ests in general, and reported more hobbies than the con- 
trol group. XlQ]lectiQns were also more common among 
the^gifted. A quesaoaaaije, on play information showed 

child of io knows " more"' - about 

plays and games than the average chnd'of 13. "Apart 
from the fact that the play interests of the gifted children 
were more mature than those of the control children of 
their own age, no conspicuous differences were found in 
their play activities. 
In character^^.d'^sonality development, the rifted 

"^'"Wi^wiwwm** 19 * 1 **^ nt Wkf*,B.i,a,j^ifaiA_*ji.^'i<iriM! MB *W.>M**'' ,, 

children were also found to be in advance of the normal. 


istered to 150 subjects, the average score was practically 
identical with that obtained at the first testing. On tests 
of fairmindedness, social intelligence, and other similar 
traits, the group proved to be markedly superior to the 
norms. Leadership and ability to cooperate in social 
enterprises were manifested more frequently in the gifted 
group than among normal subjects. Terman reports 
that: "The gifted subjects take part in a wide variety 
of extra-curricular activities and are as likely to gain 
recognition in any one of several kinds of non-academic 
activity as they are in scholarship" (32, p. 132). Simi- 
larly 84% of the boys and 90% of the girls were reported 
by parents and teachers as possessing "good general 
health" and only i% of each sex were said to be in 
"poor health." 

From the evidence examined in, this .chapter, it is appar- 
enj that there is no basis in fact for many of the popular 
prejudices regarding genius. Insanity and pathological 
conditions, rather than being characteristic of genius, are 
somewhat less common among the intellectually ablest 
than among the normal. Nor are ill health, physical 
weakness, and narrow specialization common attributes 
of genius. Most men of genius display superior talent 
from an early age; and conversely, gifted children tend 
to develop into superior adults. The environmental 
conditions of early childhood have been found to exert a 
profound influence upon the development of genius. Such 
influences may operate either through direct intellectual 
stimulation or through the establishment of motivational 
tendencies and potent interests which will spur the indi- 
vidual on to overcome obstacles and to reach a difficult 



1. Adler, A. The Neurotic Constitution. N. Y.: Moffat Yard, 
1917. Pp. 456. 

2. Brimhall, D. R. "Family Resemblances among American 
Men of Science," Amer. Naturalist, 1922, 56, 504-547; 1923, 
57, 74-88, 137-152, 326-344. 

3. Castle, C. S. "A Statistical Study of Eminent Women," 
Arch. PsychoL, No. 27, 1913. Pp. 90. 

4. Cattell, J. McK. A Statistical Study of American Men oj 
Science: III. Science, 1906, N. S. 24, 732-742. 

5. . "Families of American Men of Science," I: Pop. 

Sci. Mo., 1915, 86, 504-515; II: Sa. Mo., 1917, 4, 248-262; 
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6. Cattell, J. McK., and Cattell, J., ed. American Men of Sci- 
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8. Cox, C. M. Genetic Studies of Genius: Vol. II, The Early 
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9. de Candolle, A. Histoire des sciences et des savants depuis 
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10. Dooley, L. "Psychoanalytic Studies of Genius," Amer. /. 
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n. Eells, W. C. "The Center of Population of Higher Educa- 
tion," Sch. and Soc., 1926, 24, 339-344. 

12. Ellis, H. A Study of British Genius. London: Hurst and 
Blackett, 1904. Pp. 300. 

13. Galton, F. Hereditary Genius. N. Y.: Macmillan, 1914. 
Pp. 379 (original ed., London, 1869). 

14. . English Men of Science. N. Y.: Appleton, 1875. 

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15. Garrison, C. G., Burke, A., and Hollingworth, L. S. "The 
Psychology of a Prodigious Child," /. AppL Psychol., 1917, 



16. Hall, G. S. Adolescence. N. Y.: Appleton, 1905, Vol. I. 
Pp. 589. 

17. Hirsch, N. D. M. Genius and Creative Intelligence. Cam- 
bridge, Mass.: Sci-Art, 1931. Pp. 339. 

1 8. Hollingworth, L. S. Gifted Children: Their Nature and 
Nurture. N. Y.: Macmillan, 1926. Pp. 374. 

19. . "Subsequent History of E ; Ten Years after the 

Initial Report," /. AppL Psychol., 1927, 1 1, 385-390. 

20. Hollingworth, L. S., Garrison, C. G., and Burke, A. "Sub- 
sequent History of E ; Five Years after the Initial Re- 
port," /. AppL PsychoL y 1922, 6, 205-210. 

21. Jacoby, P. Etudes sur la selection chez I' homme. Paris rAlcan, 
1904 (original ed. 1881). Pp. 620. 

22. Lombroso, C. The Man of Genius. N. Y.: Scribners, 1895. 
Pp. 370. 

23. Moreau, J. La psychologie morbide. Paris: Masson, 1859. 
Pp. 576. 

24. Nisbet, J. F. The Insanity of Genius. N. Y.: Scribners, 1912 
(original ed., London, 1891). Pp. 341. 

25. Odin, A. Genese des grands homines, gens de lettres Frangais 
modernes. Vol. I, Paris: Librarie Universitaire, H. Welter, 
ed., 1895. Pp. 640. Vol. II, Lausanne: H. Mignot, ed., 
1895- PP- 378. 

26. Pintner, R. Intelligence Testing: Methods and Results. 
N.Y.: Holt, 1931. Pp. 555- 

27. Redfield, C. L. Great Men and How They Are Produced. 
Chicago, 1915. Pp. 32. 

28. Terman, L. M. "The Intelligence Quotient of Francis 
Galton in Childhood," Amer. /. PsychoL, 1917, 28, 209-215. 

29. Terman, L. M., and Burks, B. S. "The Gifted Child. 5 ' Ch. 19 
in Handbook of Child Psychology. C. Murchison, ed. Wor- 
cester, Mass.: Clark Univ. Press, 1933. Pp. 956. 

30. Terman, L. M., and Fenton, J. C. "Preliminary Report of 
a Gifted Juvenile Author," /. AppL PsychoL, 1921, 5, 

31. Terman, L. M., et al Genetic Studies of Genius: Vol. L 


Mental and Physical Traits of a Thousand Gifted Children. 
Stanford Univ., Calif.: Stanford Univ. Press, 1925. Pp. 648. 

32. Terman, L. M..,etal. Genetic Studies of Genius: Vol. III. The 
Promise of Youth: Follow-Up Studies of a Thousand Gifted 
Children. Stanford Univ., Calif.: Stanford Univ. Press, 1930. 
Pp. 508. 

33. Witte, K. The Education of Karl Witte (tr. by L. Wiener). 
N. Y.: Crowell, 1914. Pp. 312. 

34. Woods, F. A. Mental and Moral Heredity in Royalty. N. Y. : 
Holt, 1906. Pp. 312. 

35. Yoder, A. H. "The Study of the Boyhood of Great Men," 
Fed. Sem., 1894-96, 3, 134-156. 

36. Twenty-third Yearbook of the National Society for the Study 
of Education, 1924. 


Specialization of function between the sexes has been 
a powerful social tradition in almost all cultural groups. 
The particular tasks assigned to each sex vary from group 
to group and are even occasionally reversed, but some 
differentiation of activity is practically universal. These 
distinctions are impressed upon the individual from early 
childhood, either by actual overt differences in training 
and play-activities, or by the more subtle but equally 
potent inculcation of traditional beliefs and ideals. It is 
apparent that in most societies the effectual environments 
of the two sexes are fundamentally diverse from an early 
age. Under such conditions, we should expect pronounced 
variation in the emotional and intellectual development of 
the two sexes. By a curious circular argument, however, 
these socially conditioned behavioral differences are attrib- 
uted to innate factors. 

The belief in hereditary sex differences in mental and 
emotional traits is an old and persistent one. It is only 
since the development of objective and quantitative test- 
ing methods that the notion of female inferiority has been 
dispelled among scientists. In the general public, this 
belief still prevails, as is manifested by the reluctance to 
open certain educational and professional opportunities 
to women and by the frequent discrimination against 
individuals on the basis of sex alone. The reasoning 
underlying such practices is that it would be futile to at- 
tempt to train men and women alike, since the existing 
differences in their behavior are so clearly apparent. This 



view, of course, fails to consider the possibility that the 
existing sex differences may themselves be the result 
of the diverse training and environment of the two 


The relative intellectual achievements of men ancJ 
women through the ages have frequently been cited a? 
evidence of a sex difference in ability. An examination of 
any biographical directory or encyclopedia shows a far 
greater number of men than women to have achieved 
eminence. And of the few women listed in such com- 
pendiums, many acquired fame through special circum- 
stances rather than through the possession of exceptional 
talent. In Ellis' study (9) of British genius, only 55 
women were included in the total group of 1030 subjects* 
Nor did the standard of eminence seem to be higher ioi 
women than for men. On the contrary, Ellis claims that 
many of the women in his group had become famous 
"on the strength of achievements which would not have 
allowed a man to play a similarly large part" (9, p. 10). 

Cattell, in a carefully drawn up list of the 1000 most 
eminent persons in the world, lists only 32 women. Of 
these, II were hereditary sovereigns and 8 became emi" 
nent through misfortune, beauty, or some other circum- 
stance. This leaves an extremely small number who may 
be said to have distinguished themselves through theif 
superior talents (5, p. 375). 

Similar results were obtained by Castle (4) in her sta- 
tistical study of eminent women. A total of 868 names of 
women were collected, representing 42 nations and cover- 
ing a wide range of epochs from the seventh century B.C. 
to the nineteenth century. The largest number of women in 
the group achieved eminence through literary pursuits, 337 


or 38.8% of the subjects being classified in this field. The 
highest degree of eminence, however, as indicated by the 
number of lines allotted to the individual in standard 
biographical directories, was obtained by women as 
sovereigns, political leaders, mothers of eminent men, and 
mistresses. Among the other non-intellectual factors 
through which women achieved fame in the past are 
listed marriage, religion, birth, philanthropy, tragic fate, 
beauty, and " immortalized in literature." 

In interpreting these results, Castle seems to recognize 
certain environmental influences. Thus she states: "It is 
probable that woman has had more opportunity in litera- 
ture than in any other line of work. Her actions have been 
restricted in various degrees at different times, and in dif- 
ferent localities, and, to a certain extent, her thought has 
been regulated" (4, p. 41), In spite of this assertion, 
however, Castle suggests on the following page that, 
"the common concept of woman as a creature of feeling 
rather than a creature of reason may not be without 
foundation. If this conception is just, our classification 
tends to show that when woman has attained eminence, it 
has not been in spite of her femininity, but rather be- 
cause of it" (4, p. 42). Since both the qualifications for 
"eminence" and the attributes of "femininity" are cul- 
turally determined, such a conclusion is rather redun- 

In more recent times, the discrepancy in number of 
men and women who have distinguished themselves in 
intellectual pursuits is still large, although constantly 
diminishing. In the 1927 edition of American Men of 
Science (cf. 6, p. 1264), there were listed 725 women out 
of a total of 9785 entries in the pure sciences. The percent- 
age of women in the various fields ranged from 2.1% in 
physics to 22% in psychology. In the group of 250 scien- 


is ts who were " starred" * in the 1933 edition, only 3 women 
vere included (6). 

It is obviously impossible to draw any conclusions re- 
garding the innate abilities of the two sexes from such 
:omparisons. The recorded differences in achievement 
:ould be fully accounted for in terms of the environmental 
renditions which have prevailed. Many types of occupa- 
ions have been completely closed to women until recently. 
Thus, on the basis of their sex alone, women have been 
effectively barred from achieving eminence in a number 
>f fields. When women have eventually been admitted 
officially to such vocations, prejudice and discrimination 
igainst them have still been so prevalent that only a few 
:ould succeed. Even today, competition is not on an 
iqual basis for men and women in most occupational fields. 

Educational opportunities 2 have likewise been very 
lissimilar for the two sexes, although at present the en- 
vironments of the two sexes are more nearly equated in 
:his respect than in any other. Institutions of higher 
earning were slow to open their doors to women. Al- 
:hough America was in advance of most other countries 
n the education of women, until nearly the middle of the 
lineteenth century there was not a single institution of 
;ollegiate rank in this country which admitted women. 
Professional and post-graduate education was not avail- 
able until a much later date. Even in the elementary and 
secondary schools, the traditional curriculum of girls was 
different from that of boys, including much less science 
and more literature, art, and other "genteel" subjects. 

Nor can general home influences be disregarded. Even 

1 The starred men of science represent approximately the 1000 most eminent 
scientists in the country. The original 1000 were selected in 1903; 250 additions 
were made in 1933, similar additions having been made at successive five-year 



in the most enlightened and progressive homes, differ- 
ences are introduced in the environments of boys and 
girls which may prove very important in determining 
subsequent development. In general, girls are considered 
weaker and more frail than boys; they are sheltered more 
and are taught to be neater and quieter than their brothers. 
Boys and girls are given different toys to play with and 
different books to read. All of these apparently minor 
environmental factors, operating constantly and from a 
very early age, may exert a lasting influence upon the 
development of the child's interests, emotional character- 
istics, and intellectual talents. 

Finally, the relatively intangible but highly effective 
factor of social expectancy should be mentioned. This 
operates to perpetuate all group differences, once they 
have been established. What is expected of an individual 
is a powerful element in the determination of what he 
will do. When such expectation has the force of social 
tradition behind it and is corroborated at every instant 
by family attitudes, everyday contacts in work and play, 
and nearly all other encounters with one's fellow-beings, 
it is very difficult not to succumb to it. As a result, the 
individual himself usually becomes convinced that he is 
"superior" or " inferior," or that he possesses this or that 
talent, interest, or attitude, according to the dictates of 
his particular culture. 

During the last decade of the..&ineteentk ceatuxv, the 

^pjes^g^^ * ' 

doctrine , of ^j^^ife 1 be- 

came prominent. It was pointed out that, although the 
average ability of men and women might be equal, the 

1 The possibility of greater male variability in physical traits was originally 
alluded to by Darwin, although he does not seem to have considered the problem 
of great importance (cf, 20). 


distribution of ability in one sex might cover a wider 
range than in the other. Thus it was suggested that the 
variability of intelligence among males is greater than 
among females, there being more men than women at 
either extreme of the distribution. These hypothetical 
distributions are illustrated in Figure 46. It will be noted 



-* Measure of Intellect - *- 


that, theoretically, the averages of two groups can be 
identical while the ranges differ considerably. 

Tlxedoctrine of greater male variability was regarded 

-*~-^^ ',., , ( ,,'"' '!,"" ., '" " t'/'t' '"" n.WS'ii*/*.'*,^ V""' -- 1 

as a fundamental biological law and wa^ .believed^ t w hold 

well & ^ejatalft 
of .its,, chief protagonists, wrote as follows: 

From an organic standpoint, therefore, women represent 
the more stable and conservative element in evolution (8, 
p. 421) ... in men, as in males generally, there is an organic 
variational tendency to diverge from the average, in women, 
as in females generally, an organic tendency, notwithstand- 
ing all their facility for minor oscillations, to stability and 
conservatism, involving a diminished individualism and vari- 
ability (8, p. 425). 

This doctrine enjoyed a long popularity and was ac- 
cepted by several psychologists in their analysis of sex 
differences (cf., e.g., 5, 24). The evidence offered in sup- 
port of the greater intellectual ykriability of tKe , 


two-fold. On the one hand, the statistics on eminence 
were cited as proof of the greater frequency of superior 
intellect as well as of the presence of more extreme posi- 
tive deviations among the male sex. Similar data were 
introduced to establish the wider range of male intelli- 
gence at the lower end of the distribution. Surveys of 
institutions for the feebleminded in several countries re- 
vealed a consistent excess of males among the inmates. 
Thus it was argued that there were more idiots as well as 
more geniuses among men, and that women as a group 
tended to cluster more closely around the average or 
mediocre degrees of ability. 

The cultural basis of sex differences in the attainment 
of eminence has already been discussed. No biological 
law need be invoked to account for the greater frequency 
of men in the biographical directories and encyclopedias. 
The greater incidence of males in institutions for mental 
defectives has : likewise beeiTlound to result 'from cultural 
~fa50*9 This was especially ^ggjonstrated in a study by 
1*. L S. , Hollingworth (14) on 1000 cases referred for exam- 
ination to the Clearing HSuse for Mental Defectives at 
the Post Graduate Hospital in New York City, as well as 
1142 cases actually committed at the New York City 
Children's Hospital. 1 Analysis of intelligence test scores 
and other available data revealed the differential opera- 
tion of a selective factor upon the two sexes. 

In the first place, the males referred for examination, as 
well as those actually committed, were on the average 
much younger than the females. Secondly, the I.Q.'s of 
the females presented for examination were lower than 
those of the males. This difference in LQ. was even greater 
when the cases actually committed were compared. A 

1 An institution for mental defectives, then located at Randall's Island, 


survey of the previous occupations and general case his- 
tories of the subjects suggested that the probable explana- 
tion ofj:hese findings lies in the uncompetitive nature of 
many occupations open to women. ^nugjg^^^titfi..dettec- 
Tion of feeblemindedness as well as the necessity of com- 
mitment less.likely among women than among men. A 
woman of moron level can survive outside of an institu- 
tion by turning to housework, prostitution, or marriage as 
a means of livelihood. The boy, on the other hand, is 
forced into industrial work at a relatively early age and 
will soon reveal his mental deficiency in the severe com- 
petition which he encounters. Thus, although there is an 
excess of males in institutions for mental defectives, it 
^would seem that there are more feebleminded females 
outsicte of institutions. 

'" "ttarl Pearson (20) was among the first to challenge the 
adequacy !j5Ot33535&. s$x differences in 
a comparison of the extremes of the distribution. He 
called """attention to the need for direct measurement of 
variability around the average in large groups of unselected 
subjects. Pearson himself computed coefficients of rela- 
tive variability for several classes of data, consisting 
chiefly of physical and anatomical measurements on 
adults. He found no evidence of greater male variability, 
but rather a slight tendency to greater female variability. 
Similarly ^JHbUiogworth and Montague (15) collected a 
krge^nu^mber of jAysica^ 0^^,jqQp"mif e 

andjooa, Jemale,,,ijafaat& , M ^irth^^ 

possible effects of differential environment. No consistent 

r, , .-<-'^^^^^^ 

sex dmerence in variability was found. 

^^iri^s'^^^tS^^nSw'' available on male and female 
variability in a wide variety of traits. 1 In such character- 

1 For summaries of a large portion of this material, cf. Henmon and Living* 
pAone (13) and Lincoln (17). 


istics as height, weight, physiological maturity, dentition, 
and anatomical development, the data are inconsistent. 
The relative variability of the two sexes differs with the 
specific trait under consideration, the age of the subjects, 
their social and economic level, and even the particular 
community in which the data are obtained. Intelligence 
test results exhibit a similar lack of consistency. On indi- 
vidual tests such as the Stanford-Binet, girls seem some- 
what more variable, whereas boys show wider variability 
on many group tests. Age is also a factor in determining 
the relative variability of the sexes on these tests. 
The same is true of variability In school achievement. 
The findings differ with the specific situation, in one case 
the boys being more variable, in another the girls. In the 
large majority of cases, furthermore, the differences in 
variability in favor of either sex are too slight to be of 
much significance. 


In all group comparisons, selective factors may operate 
to vitiate the results. When a group is not a random or 
representative sample of the population from which it is 
drawn, it is said to be a select group. Such a sampling is 
unsuited for any type of investigation, since any results 
obtained with it could not be generalized but would apply 
only to the specific group employed. An additional com- 
plication in the comparison of two populations arises 
from the fact that selection may have operated differently 
in the two groups. Thus if a group of college girls were 
compared with trade school boys, the two samplings would 
be selected in different ways. Not only is neither group 
representative of men or women in general, but the one 
represents the upper end of the female distribution and 
the other a central or slightly inferior segment of the male 


distribution. In addition to being unrepresentative, these 
groups are not comparable. 

Selective factors are often difficult to detect and usually 
difficult to control. An example of a selective factor whose 
presence was repeatedly overlooked is furnished by the 
data on the relative incidence of males and females in 
institutions for the feebleminded (cf. above). A similar 
selective influence has been demonstrated in high school 
enrollment. It would seem that groups of boys and 
girls attending the same high school constitute truly 
comparable samples for the study of sex differences. But 
investigations on elementary and high school students 
have demonstrated that this is not the case. 

In two separate studies, the Pressey Group Test of 
intelligence was administered to 2544 elementary school- 
children between the ages of 8 and 16 (22) and to 5929 
high school seniors ranging in age from 16 to 23 (3). The 
percentages of boys who reached or exceeded the median 
score of the girls, as well as the number of cases in each 
group, are shown below. In the elementary school study, 
the data are reported separately for each age group (cf . 22, 
p. 327). In the study on high school seniors, a single 
summary figure is given for the entire group (cf. 3, p. 61). 

Elementary School Group 


of Cases 













I6 7 






1 02 


High School Seniors 




< Exceeding Girls' Median 




It will be noted that in the elementary school grades the 
girls excel at all ages, although the sex difference is negli- 
gible among the i6-year-olds. Among the high school 
seniors, however, this relationship is reversed, over 50% 
of the boys reaching or exceeding the girls 5 median score. 
This reversal becomes intelligible if we examine the 
relative number of each sex in the elementary grades and 
in the senior year of high school. Throughout the high 
school period there is a much more rapid elimination of 
boys than girls. Boys whose academic work is not satis- 
factory are more likely to leave school and go to work, 
whereas girls tend to be kept in school longer. Girls 
also seem to adjust better to the school curriculum and 
school routine in general. The less intelligent girls will 
exert more effort and manage to pass sufficient subjects to 
stay in school, while boys in the same situation are more 
likely to rebel against school work. This explanation was 
borne out by an examination of the scholastic history of 
those students who had dropped out in the course of their 
high school work. Owing to the differential action of this 
selective influence upon the two sexes, differences between 
the intelligence test scores of high school boys and girls can- 
not be attributed to a true sex difference. In the evaluation 
of any study on group differences, selective factors are one 
of the most subtle forms of error to be guarded against. 


A further complication in the analysis of sex differences 
arises from a difference in the developmental rate of boys 
and girls. Itjias been clearly established that in physical 
characteristics girls reach maturity earlier than boj;s. 
Moreover, at any one age (luring childhood, girls are 
usually farther advanced towards their ultimate adult 
status than boys. 


Several investigators have compared the height and 
weight of boys and girls at successive ages. In order 
directly to compare the developmental status of the two 
sexes in these traits, each age average can be expressed 
as a percentage of the adult norm for that sex. In 
Table XVI will be found such percentages for boys and 
girls between the ages of 6 and 17. The figures are based 
upon data from several investigations. It will be noted 
that at each age measured, the girls have attained a greater 
percentage of their adult height and weight than the boys. 
Similar results were obtained in an extensive investigation 
by Baldwin (2), in which the same subjects were measured at 
successive ages. At certain ages the developmental acceler- 
atToonoFfKie girls is so great that they are actually taller &nd 
heavier than boys, in absolute measures. In Baldwin's data, 
the girls were found to be superior in height between the 
ages of ii and 13, and in weight between 9 and 16. 



(After Lincoln, 17, p. 20) 



































































Other aspects of physical development show a similar 
acceleration of the female sex. It is a well known fact 
that girls reach the age of reproductive maturity earlier 
than boys. In two investigations (7, i) on about 4800 boys 
and 1241 girls, respectively, the Children were classified 
into pubescent and post-pubescent on the basis of several 
physiological observations. The average age at which the 
girls entered the post-pubescent stage was between 13 and 
13!; the boys reached this stage approximately one year 
later. Except at age 16, the percentage of girls in each 
a g e group who were classified as post-pubescent exceeded 
the percentage of boys so classified by a substantial 


Anatomical development has been measured by the 
relative degree of ossification of the bones of the hand. 
In this also, girls have been found to be in advance of 
boys, the median anatomic indices of the girls being higher 
than those of the boys at every age from 6 to 1 6 (cf. 21), 
A similar difference has been found in dentition. In gen- 
eral, girls shed their deciduous teeth sooner and get their 
permanent teeth at an earlier age than boys. In the case 
of certain teeth, these differences amount to one year or 
over (cf. 12). 

The significance of sex differences in the rate of physical 
growth has been emphasized by several writers (cf., e.g., 3, 
17, 22). It has been suggested that girls might be acceler- 
ated in mefttal as well as physical development. Thus the 
'fact that girls of elementary school age excel on most 
intelligence tests has been attributed to this factor. If 
this were the case, equated age groups of boys and girls 
would not be comparable. It would then be necessary to 
equate the sexes in regard to developmental stage or 
physical maturity rather than chronological age. But 
such a procedure would introduce an inequality in amount 


of training and general environmental stimulation. This 
problem only arises, of course, in the comparison of chil- 
dren, and does not apply to adults. Children, however, 
have been the most frequent subjects for surveys on sex 
differences, both because of their greater accessibility 
in large numbers and because they have been exposed to a 
relatively more homogeneous environment. 

It should be noted that mental acceleration of girls 
has lioFTTeen directly demonstrated. Its possibility has 
only been inferred by analogy with physical development. 
It is doubtful, however, whether physical maturity can 
have much influence upon intellectual development. The 
data on the relationship of mental and physical traits are 
too consistently negative for such an assumption (cf. 
Ch. VIII). In emotional and other personality traits it is 
probable that the onset of puberty and the relative physio- 
logical maturity of the individual introduce a disturbing 
factor in sex comparisons at certain ages. But in regard to 
the child's intellectual status, the environmental stimula- 
tion to which he has been exposed is far more significant 
than slight differences in physical condition. 


In the evaluation of any obtained difference between 
two groups, it is necessary to determine the statistical 
reliability of such a difference. Reliability means, in this 
case, the degree of consistency among the results obtained 
on different samplings of the same population. The prob- 
lem of reliability arises from the fact that in any investi- 
gation only a sample of the entire population is employed. 
For example, if the population under investigation is 
defined as public school children in American cities, data 
may be gathered on some 5000 or 6000 children in a dozen 
schools. From these results, the investigator generalizes 


to the entire population. If the sampling was carefully 
chosen to be representative of the given population, such 
conclusions will not be far in error. The figures thus 
obtained, however, will not be identical to those which 
would have been secured by testing the entire population 
of American city public school children. Nor will the 
results from successive samplings of the population coin- 
cide perfectly. Had a different sampling of 5000 city 
public school children been employed, slightly different 
results would have been obtained. 

This variation in results from sampling to sampling 
within the same population is known as a sampling error. 
Statistical measures of reliability furnish a theoretical 
estimate of the probable limits within which such errors 
will fall. Formulae are available for the computation of 
the sampling error of all statistical measures, such as 
averages, differences between averages, measures of varia- 
bility, and correlation coefficients. It is thus possible to 
estimate the maximum amount of variation to be expected 
in any statistical measure if the experiment were repeated 
on another sampling of the same population. 

The most common measures of reliability are the "prob- 
able error" (P.E.) and the "standard error" (S.E. or <r). 
The total estimated range within which a given measure 
will fall in successive samples is covered by =b 4 X P.E, 
and =h 3 X S.E. An hypothetical example will serve to 
illustrate the application of such measures. If the aver- 
age score obtained by a group is 40 points and the P.E. 
of this average is found to be ^ points, then 

Therefore, in successive samples of the population from 
which this group was drawn, the average might fall be- 
tween 32 and 48. These extreme values will, however, 


be rare, and in one-half of the samples the average will 
probably fall between 38 and 42, or =t I P.E. from the 
obtained value. 

Similarly, let us suppose that a group of sixth grade 
public school boys and girls obtained the following aver- 
age scores on an intelligence test: 

Average Score 

Girls 90 

Boys 80 

Difference 10 

Let us assume further that the P.E. of this difference 
is 5. In different samples of sixth grade public school chil- 
dren, we should therefore expect the sex difference to vary 
from 30 points (10 + [4 X 5] = 30) to 10 points 
(10 [4X5] = 10). In other words, the relative standing 
of the male and female groups would be reversed in certain 
samplings, and the boys' average might be as much as 
10 points higher than that of the girls. This is what is 
meant by an unreliable difference. The same conclusion can 
be arrived at more directly by dividing the obtained dif- 
ference by its P.E. If the difference is 4 or more times 
as large as its P.E., there will be no reversal of direction 
and the difference is said to be perfectly reliable. In the 
present example, it will be noted that the difference is 
only twice as large as its P.E. (10 -5- 5 = 2). This value, 
called the critical ratio, is an index of the degree to which 
the obtained figures represent a reliable or consistent trend. 
TJb&.<pbA^ errpr)jof ^n ob- 

tained , , difference, 4ep wU , upqn^he ^ s ize jpT tKeTam^lings 
employed as well as tjifi amount of var^^ft^m^m^ihe 
samplings. It is apparent that the larger the sampling, the 
more reliably will the results be established. If the sam- 
pling were infinitely large, the probable error would be 
zero, since the entire theoretical population would then 


have been included. In most of the earlier investigations 
on sex differences, the samples employed were so small 
as to yield extremely large probable errors, had the latter 
been computed. The sex differences reported in such stud- 
ies may have been due entirely to chance errors of sam- 

Similarly, the wide variability existing within each sex 
in regard to any trait renders the differences between 
averages less reliable. If all women were of identical 
height, for example, and all men were likewise equal in 
height, then sex differences in height could be reliably 
established by comparing only one representative of each 
sex. All other samplings would yield the same difference, 
since variation within each sex would be zero. The greater 
the variability within either group, the larger will be the 
probable error of the obtained values. In the computa- 
tion of P.E/s and SJE/s, both the number of cases and 
the variability of the group are taken into account. 1 


The establishment of a perfectly reliable difference 
betweOT W6 "groups does i^ot preclude the possibility of a 
large amount of overlapping between, such groups. In 
Figure 47 will be found the distribution curves of a group 
of 189 boys and 206 girls in the third and fourth elementary 
school grades on a test of arithmetic reasoning. The 
average score of the boys is 40.39 and that of the girls 
35.81. The difference between the averages is 4.58 points 
and the P.E. of this difference is only 0.58. The difference 
is thus nearly eight times as large as its P.E. and can be 

i o TT S.D. of the group -n ,-, r 

1 S.E. of an average - ~2 - fT; P.E. of an average = .6745 


S.D. of the group ,,,..,,. . , , 

X - . . - . For a further discussion of the computation and use of 

these measures, see Garrett (10). 

50 r 

10- 15- 20- 25- 30- 35- 40- 45- 50- 55- 
14 19 24 29 34 39 44 49 54 59 


REASONING. (Data from Schiller, 23, p. 67.) 

regarded as perfectly reliable. An examination of the 
distribution curves, however, reveals a large amount of 
overlapping between the two groups. A very large per- 
centage of boys and girls fall within the same range of 
scores. Furthermore, 38% of the girls obtained scores 
higher than the boys' average, and 24% of the boys scored 
below the girls' average. 

Thus, on account of overlapping, any relationship estab- 
lished for the group averages will not necessarily hold for 
individual cases. Although one group may excel another 
by a large and significant amount, individuals can be 
found in the " inferior" group who will surpass certain 
individuals in the " superior" group. Owing to the large 
extent of individual differences within any one group as 
contrasted to the relatively small difference between 
group averages, an individual's membership in a given 


group furnishes little or no information about his status 
in any trait. 

In the large majority of investigations on group differ- 
ences, only averages are considered. For a complete pip- 
ture of the relative standing of the two groups, however, 
some index of the degree of overlapping should be in- 
cluded. The best procedure would be to report the entire 
frequency distributions of the two groups. This is often 
impracticable, however. A simpler alternative, in the case 
of normally distributed samplings, is to state the per- 
centage of subjects in one group who reach or exceed the 
median (or average) of the other. Complete overlapping 
would then be indicated if 50% of one group reached or 
exceeded the median of the other. 1 If more than 50% of 
group A reach or exceed the median of group B, then 
group A is superior to group B; if less than 50%, A is 
inferior to B. Occasionally, some other value is substituted 
for the median as the point of reference. Thus the in- 
vestigator might report the percentage of group A which 
reaches or exceeds the highest score obtained in group B, 
or the percentage of group A which reaches or exceeds 
the upper quarter of group B. 


It is a platitude to insist that, in order to obtain sig- 
nificant data on any question, an accurate measuring 
instrument must be employed. Yet the methods of 
measurement employed in the study of sex differences, 
as well as in other group comparisons, have frequently 
been crude and often wholly unsuited to the problem. 
Thus ratings by associates were used in many of the 

1 The curves will not coincide, of course, if the ranges are unequal. In such a 
case, complete overlapping is obtained only in the sense that one distribution is 
contained entirely within the other. 


earlier investigations on sex differences, and especially 
in those concerned with personalty traits. Teachers' 
ratings of schoolchildren were especially common. It is 
obvious that such ratings do little more than reflect the 
systematic bias of the judges. In the comparison of such 
groups as the sexes or various "races" or nationalities 
about which definite beliefs are fostered within each cul- 
ture, ratings cannot be regarded as an index of the sub- 
ject's actual standing. 

The reliability of the tests should also be considered. 
If a test is too short or if performance on it is affected by 
too many irrelevant factors, it will yield different results 
on repeated administrations. On such a test, the scores 
of the same individuals will vary widely from time to 
time. These discrepancies in test scores are known as 
errors of measurement. Group differences found with a 
short and poorly constructed test may be entirely spurious 
and may be expected to disappear upon a reexamination 
of the same subjects. 

Much confusion has also been introduced into discus- 
sions of group differences by the relatively loose designa- 
tions assigned to most mental tests. If a test is labeled 
"analytic reasoning," there is a tendency to assume that it 
actually measures that trait, although such a trait may 
not even exist as a unitary function and may consist of a 
manifold of independent abilities. Similarly, if two tests 
are given the same name, they are commonly regarded as 
measuring the same function. An hypothetical example 
will show how this practice may affect group comparisons. 
Let us suppose that one investigator has constructed a 
sentence completion test, which he labels a measure of 
"logical thinking." In such a test, as in most verbal 
tests, girls will probably excel. If now another investi- 
gator also sets out to construct a test of "logical thinking" 


and decides to employ arithmetic problems as his material, 
he will find that boys excel in this trait. The results of the 
two studies will thus seem to be in direct contradiction, 
owing to the use of a common term to cover two discrete 
types of mental activity. 

Many discrepancies in the data on sex differences may 
be attributed simply to such a confusion of terminology. 
Unless identical tests are administered in an identical 
manner, we cannot assume that the same mental processes 
were measured in every case. The use of a different time 
limit, for example, might change a power test into a speed 
test and thus yield entirely different results. A slight 
alteration in the directions might make it more difficult 
for the subjects to understand what is required of them 
and might thereby introduce a new element into the test, 
viz., ability to follow verbal instructions. "Intelligence" 
scales are probably the best example of the use of general 
terms in describing widely diverse tests. Much con- 
troversy has been occasioned by the application of such 
scales. Owing to the employment of "intelligence" scales 
which sample different sets of abilities, some students of 
sex differences conclude that boys are more intelligent, 
others that girls are more intelligent. 

A closely related problem pertains to the use of "lump 
scores" in group comparisons. Group differences in 
specific abilities may be completely obscured by the com- 
parison of total or average scores on a battery of tests. 
If, for example, boys excel in numerical aptitude and girls 
in verbal aptitude, and a scale of 'so-called general in- 
telligence is weighted equally with items from both fields, 
no significant sex difference in total score will be found. 
Should the scale be overweighted with items of one type, 
furthermore, it will favor the group excelling in that 
trait and indicate an apparent difference in general in- 


telligence. In recent years, with the development of a 
more critical attitude towards mental testing, there has 
been a growing tendency to look for group differences in 
separate abilities rather than in " general level of perform- 
ance." In the study of group differences, it is of the great- 
est importance to state results in highly specific terms 
and to limit conclusions to the particular materials, 
procedure, and other conditions of each investigation. 1 


The most crucial problem in any analysis of group 
differences pertains to their origin. The theoretical and 
practical implications of behavioral characteristics which 
are innately fixed and of those which are socially condi- 
tioned are fundamentally different. The question of 
heredity and environment is always a difficult one to 
answer. It is especially elusive in the case of human 
development because of the practical impossibility of 
rearing children under rigidly controlled laboratory condi- 
tions. And as was shown above, we cannot otherwise 
assume that the environments of the two sexes have been 
equated, even in the case of fraternal twins. 

There are, however, certain indirect sources of evi- 
dence which throw some light upon the origin of group 
differences. Thus a biological or hereditary determination 
of sex differences in ps^cfi'^ the 

existence of a universal pattern of male and Jemale behavior. 
If, ori the other hand, such differences are environmentally . 

conditioned, we should expect the traditional ]behavioral 
\ ^, f8Brw ^^w^ 

characteristics of each sex to ptfr^ JT<^^ 

D*ata on this question are as yet relatively meagre. 

Psychologists have generally neglected the wealth of infor- 

1 For a further discussion of many of the difficulties involved in the study of 
sex differences, see Lehman and Witty (16). 


matlon offered by the comparative study of behavior 
phenomena in different cultural milieux. Certain facts 
collected by anthropologists, however, have a direct bear- 
ing upon this problem. 

The play activities of boys and girls have been a sub- 
ject of frequent speculation. Some would argue, for 
instance, that girls play with dolls because of a nascent 
" maternal drive" or some similar innate interest or emo- 
tional trait characteristic of their sex. The almost com- 
plete absence of this type of play activity among boys is 
regarded as an index of a fundamental biological diversifi- 
cation in emotional response. An observation made by 
Mead (18) in her studies on the island of Manus in New 
Guinea is of interest in this connection. Dolls are ordi- 
narily unknown to the children on this Island. But when 
they were presented for the first time with some wooden 
statuettes, it was the boys and not the girls who accepted 
them as dolls, crooning lullabies to them and displaying 
typical parental behavior. This reaction is to be under- 
stood in terms of the pattern of adult behavior in Manus. 
Owing to the traditional division of labor, the women 
are busy with their various duties throughout the day, 
while the men have much more leisure time between their 
activities of hunting and fishing. As a result the father 
rather than the mother attends to the children and plays 
with them. This socially established differentiation of 
behavior was reflected in the play responses of the boys 
and girls. 

A vivid demonstration of the cultural determination of 
behavior is furnished by a more recent study of Mead (19) 
in which she observed the traditional emotional char- 
acteristics of men and women in three primitive societies 
in New Guinea. Each of these groups presented a different 
pattern of male and female personality. Among the 


Arapesh both men and women displayed emotional 
characteristics which in our society would be labeled 
distinctly feminine. In this group both sexes are trained 
to be cooperative, unaggressive, gentle, non-competitive, 
and responsive to the needs of others. They are strongly 
imbued with a sense of obligation towards any who are 
weaker or younger than themselves. Even their typical 
response towards material objects is not one of possession 
but of solicitude. 

The MundugumuT) a river-dwelling tribe of cannibals 
and head-hunters, present a sharply contrasting picture. 
In this society both men and women are violent, aggres- 
sive, ruthless, and competitive. They take great delight in 
action and in fighting. They are quick to perceive an 
insult and ever ready to avenge it. Because of an intricate 
system of family organization, the child is born into a 
hostile world, in which most members of his own sex are his 
enemies. This is particularly true of boys, but a child of 
either sex will be disliked and resented by some members 
of the family. 

Perhaps the most interesting pattern is presented by the 
Tchambuli) among whom there is a genuine reversal of 
the sex-attitude of our culture. It is the women who have 
the position of power in Tchambuli. The group depends 
for its food supply upon the fishing of the women, the men 
rarely engaging in this activity. Fish is also the staple 
product of trade, in exchange for which several essential 
commodities are obtained. Similarly, it is the women who 
make mosquito bags, the most important article of 
Tchambuli manufacture and in great demand by outside 
purchasers. The men, on the other hand, engage predomi- 
nantly in artistic and non-utilitarian pursuits. Most men 
are highly skilled in more than one art, including dancing, 
carving, painting, and others. It is the man in this society 


who is concerned with the beauty and elaboration of his 
costumes and the excellence of his artistic accomplish- 
ments. This type of life is reflected in pronounced per- 
sonality differences between the sexes. The women are 
impersonal, practical, and efficient. Their attitude towards 
the men is one of kindly tolerance and appreciation. The 
men are graceful, artistic, emotionally subservient, timid, 
sensitive to the opinions of others, and throughout their 
lives dependent upon the security afforded to them by the 

Each of these three cultures has its "deviants, 33 its 
maladjusted individuals whose personality traits clash 
with the accepted standards, as in our society. But the 
deviant in one society often coincides with the traditional 
ideal of another. Thus the "masculine" woman among 
the Tchambuli is one who embodies the typically feminine 
characteristics of our society; the "effeminate" Tchambuli 
man displays behavior which we should characterize as 
typically masculine. These observations inevitably sug- 
gest an environmental interpretation. In a final evaluation 
of her findings, Mead writes : 

We are forced to conclude that human nature is almost 
unbelievably malleable, responding accurately and contrast- 
ingly to contrasting cultural conditions. The differences 
between individuals who are members of different cultures, 
like the differences between individuals within a culture, are 
almost entirely to be laid to differences in conditioning, es- 
pecially during early childhood, and the form of this condi- 
tioning is culturally determined. Standardized personality 
differences between the sexes are of this order, cultural cre- 
ations to which each generation, male and female, is trained 
to conform (19, pp. 280-281). 



1. Baldwin, B. T. "A Measuring Scale for Physical Growth 
and Physiological Age," Nat. Soc. Stud. Educ., Fifteenth 
Yearbook, 1916, Part I, 11-22. 

2. . "The Physical Growth of Children from Birth to 

Maturity," Univ. Iowa Stud. Child Welfare, 1921, I. Pp. 411. 

3. Book, W. F., and Meadows, J. L. "Sex Differences in 5925 
High School Seniors in Ten Psychological Tests," /. AppL 
PsychoL, 1928, 12, 56-81. 

4. Castle, C. S. "A Statistical Study of Eminent Women," 
Arch. Psychol., No. 27, 1913. Pp. 90. 

5. Cattell, J. McK. "A Statistical Study of Eminent Men," 
Pop. Sci. Mon., 1903, 62, 359-377. 

6. Cattell, J. McK., and Cattell, J. American Men of Science: 
a Biographical Directory. (Fifth edition.) N. Y.: Science 
Press, 1933. Pp. 1278. 

7. Crampton, C. W. "Anatomical or Physiological Age versus 
Chronological Age," Fed. Sem., 1908, 15, 230-232. 

8. Ellis, H. Man and Woman: a Study of Human Secondary 
Sexual Characters. N. Y.: Scribners, 1904. Pp. 488. 

9. . A Study of British Genius. London : Hurst and Blac- 

kett, 1904. Pp. 300. 

10. Garrett, H. E. Statistics in Psychology and Education. 
N. Y.: Longmans Green, 1932. Pp. 317. 

11. Goodsell, W. The Education of Women. N. Y.: Macmillan, 
1923. Pp. 378. 

12. Hellman, M. "The Process of Dentition and Its Effect upon 
Occlusion," Dental Cosmos, 1923, 65, 1329-1344. 

13. Henmon, V. A. C., and Livingstone, W. F. "Comparative 
Variability at Different Ages," /. Educ. PsychoL, 1922, 13, 

14. Hollingworth, L. S. "Differential Action upon the Sexes 
of Forces Which Tend to Segregate the Feebleminded," 
J. Abn. PsychoL, 1922, 17, 35-57- 

15. Hollingworth, L. S. 3 and Montague, H. "The Comparative 
Variability of the Sexes at Birth," Amer. J. Social, 1914-15, 
20, 335-3/0- 


1 6. Lehman, H. C., and Witty, P. A. "Sex Differences: Some 
Sources of Confusion and Error," Amer. /. PsychoL, 1930, 
42, 140-147. 

17. Lincoln, E. A. Sex Differences in the Growth of American 
Schoolchildren. Baltimore: Warwick and York, 1927. Pp. 

1 8. Mead, M. Growing up in New Guinea. N. Y. : Morrow, 
1930. Pp. 372. 

19. . Sex and Temperament in Three Primitive Societies. 

N. Y.: Morrow, 1935. Pp. 335. 

20. Pearson, K. The Chances of Death and Other Studies in 
Evolution. London: Arnold, 1897. Vol.1. Pp.388. Ch.VIII: 
"Variation in Man and Woman/' 

21. Prescott, D. A. "The Determination of Anatomical Age in 
School Children and Its Relation to Mental Development," 
Harvard Mon. in Educ., Series I, No. 5, 1923. Pp. 59. 

22. Pressey, L. W. "Sex Differences Shown by 2544 School 
Children on a Group Scale of Intelligence, with Special 
Reference to Variability," /. Appl. PsychoL, 1918, 2, 323- 

23. Schiller, B. "Verbal, Numerical, and Spatial Abilities of 
Young Children," Arch. PsychoL, No. 161, 1934. Pp. 69, 

24. Thorndike, E. L. Educational Psychology. N. Y.: Teachers 
College, Columbia Univ., 1914. Vol. III. Pp. 408. 


Since the beginning of the mental testing movement, 
there has gradually accumulated a large body of data on 
sex differences. Every type of ability has been covered, 
from sensory and motor traits, through simple perceptual 
and associative tasks, to more complex intellectual proc- 
esses and personality traits. Almost all tests, shortly 
after their construction, have been administered to mem- 
bers of the two sexes, and their scores compared. It was 
a relatively easy task to collect such data, especially 
after the advent of standardized group tests. But it 
was quite a different matter to determine what these 
data meant. Itjs now apparent that the sex differences 

^"^^^MvaawaSws- W^iwJu^ J . , ,,,,,e , ,,,, , ,,,,,,., .,,. ' "' **"*"" "'" 

foujgydjwi^ grottp reflect the social 

jraditions of that group rather than the innate .behavioral 
attributes of each sex. 

The data which will be surveyed in the present chapter 
show sex differences under existing conditions in our society. 
Such data, although limited in their application, are not 
without value. Thus it is of considerable practical inter- 
est to ascertain the typical behavioral characteristics of 
men and women, whatever their origin. The number of 
situations in which such knowledge would prove useful 
is legion. In many fields of activity, definite assumptions 
are being made in regard to existing sex differences in 
interest, emotional appeal, and similar traits. This sex 
differentiation is noticeable in advertising and selling, 
political campaigning, the organization of newspapers and 
magazines, social work, crime prevention, and the treat- 



ment of offenders, to name only a few outstanding exam- 
ples. Insofar as cultural conditioning may have produced 
certain clear-cut sex differences, these cannot be ignored 
in the practical adjustments of everyday life. In a descrip- 
tive account of any one cultural group, the question of 
sex differences in behavior can be legitimately raised. 

It is also possible that a careful analysis of the material 
on sex differences, in conjunction with other available 
information, may throw further light upon the nature 
and genesis of such differences. Such an approach .can 
never furnish a conclusive account of the origin of sex 
differences, but it may indirectly yield some corroborative 
evidence on this problem. 

In surveying the vast array of studies on sex differences 
in each type of behavior, the general trend of the results 
will be reported. In addition, a few of the best illustrative 
studies in each fielcl will be cited. No attempt has been 
made to present a complete survey of investigations on 
this topic, since such material has been frequently and 
extensively reviewed by various writers. 1 

In view of the problems discussed in the preceding 
chapter, such as selective factors, extensive overlapping 
of groups, errors of sampling, errors of measurement 
arising from inadequacy of the tests, and unwarranted 
generalizations regarding the functions measured, it would 
seem very difficult to formulate any summary statements 
regarding sex differences from the data of a number of 
independent investigations. This is especially true since 
such investigations differ widely in number and kind of 
subjects, specific tests or materials employed, and other 
important conditions. Similarly, all but the most recent 

1 Cf., e.g., Allen (i), Goodenough (12), L. S. Hollmgworth (18, 19), Lincoln 
(26), Loutitt (27), Wellman (52), Woolley (57, 58), and the more recent and 
very comprehensive review by Miles (31). 


and best controlled studies fail to report reliabilities of 
differences, degree of overlapping, and other essential 
facts, thus making it difficult to evaluate their findings. 
In the face of these conditions, the only available criterion 
for the acceptance of a conclusion is the consistency of 
results of different investigators. A survey of the experi- 
mental literature on sex differences reveals certain major 
findings which are so frequently reported by different 
investigators as to suggest a valid basis in fact. It is 
with these findings that we shall be primarily concerned. 


Sex differences in sensory capacities are very slight, 
a p<;pgQfln^ few. In color discrimination, 

most investigators find women slightly superior (49, 53), 
a fact which may be related to the more frequent practice 
which women have had in the use of color, as in dress, 
household decorating, and embroidery. Color blindness is 
also less common in the female, having been observed in 
about 4% of men and only 0.5% of women (53). In 
hearing, there seem to be no significant sex differences. 
Although several early investigators reported female su- 
periority in pitch discrimination, more accurate experi- 
ments by Seashore (41) have demonstrated the absence 
of any such difference. In taste and smell, the data 
are too conflicting to allow any summary statement of 
sex differences. 

In the discrimination of lifted weights, men have gener- 
ally been found to excel slightly (53), This difference 
has sometimes been attributed to the better development 
of motor ability in general among men (cf. 49). On 
standard tests of sensitivity to pain, women obtain lower 
average thresholds. Thus in experiments in which pain 
was induced by a steadily increasing mechanical pressure 


on the skin, women report a sensation of pain on the aver- 
age sooner than men. It is interesting to note that in 
one investigation (n) this difference was found to increase 
with age, until at the age of 1 8 or 19 it became over one 
kilogram. In experiments on college students (56), the 
average pressure at which pain was reported was 5.9 kg. 
for men and 2.4 kg. for women. It should be noted, of 
course, that such tests rely upon the subject's report of 
pain. The results are therefore open to the influence of 
social tradition and habits of endurance. In two-point 
threshold, i.e., the shortest perceptible distance between 
two points on the skin, women have also been found to 
have a finer discrimination (53). In the discrimination 
of temperature, degree of pressure on the skin, and other 
aspects of tactual sensitivity, no clear-cut sex difference 
has been demonstrated (53). 

In regard to motor tasks, some reviewers (cf., e.g., 58) 
have ventured the conclusion that boys excel in speed 
and precision of movement in tasks in which the direction 
of attention remains fixed, whereas girls excel in tasks 
requiring rapid adaptations of response and shifts of 
attention. This generalization, although probably correct 
in most cases, is not without exception. In speed of tap- 
ping, most experimenters report male superiority. Thus 
Thompson (49) found 88% of the men reaching or exceed- 
ing the median tapping rate of the women. Burt and 
Moore (6) reported that 69.8% of the boys reached or 
exceeded the girls* median. But a few investigators have 
found a slightly faster tapping rate among women, prob- 
ably owing to affective attitudes and motivational factors 
introduced by the conditions of the experiment (cf. 53, 
I, p. 140). Men have been found to have a shorter and 
somewhat more consistent reaction time than women. 
In coordination tests, such as aiming and tracing, boys 


generally excel. Two functions in which a very consistent 
female superiority is reported are mirror drawing and 
cancellation, both involving rapid shifts of attention and 
adaptation to a new mode of response (53). 

The relation of these findings . to the traditional play 
activities of the two sexes is apparent. Boys' games offer 
frequent opportunities for the development of rapid and 
well-coordinated movements* Finer adjustments of more 
restricted muscle groups, on the other hand, are more often 
involved in the activities of girls. 


A^ljgh^but highly consistent male superiority on tests 
of mechanical or spatial ^aptitudes has, been, establish^- 
Iri^Thompson's pioneer investigation (49) on adult men 
and women, two mechanical problems were included in 
the series of tests. In both of these, the subject was to 
determine the method of operation of rather complex 
mechanical contrivances. The average amount of time 
required for the solution of each problem by the male 
subjects was considerably shorter than that required by 
the female subjects. Similar results have been obtained 
in practically all subsequent studies with spatial tests. 
In the solution of puzzle-boxes, as well as in a variety 
of form-board tests, in which the subject is to insert 
blocks of different shapes into the correct recesses, boys 
required less time on the average and had fewer failures 
within the allotted time limit than girls. In performance 
on a slot maze, boys were also found to excel markedly 
(cf. 12). 


&X iQwXSp^ 

with girls of the same Stanford-Binet I.Q. Porteus 
regards this finding as indicative '" oFTTex" 3itference in 


planning capacity, foresight, and similar personality traits 
which he believes to be measured by his maze tests. It 
seems more probable, however, that the obtained differ- 
ence on the two tests is owing to the boys' superiority in 
spatial ability and the girls' superiority in verbal ability, 
the latter playing a large part in performance on the 
Stanford-Binet. Similar results were obtained by Goode- 
nough (12) who administered the Wallin Peg Board 
test to 100 children between the ages of 2 and 4. In this 
test the subject is required to insert variously shaped 
pegs into the appropriate holes as rapidly as possible. 
A consistent sex difference was found in favor of the 
boys, although the same group yielded a reliable difference 
in favor of the girls in Kuhlman-Binet I.Q. 

In a study (30) designed to measure " practical ability," 
a series of ten tests was administered to 172 boys and 
184 girls between the ages of 10 and II, all of whom were 
attending English schools. The tests included four con- 
struction tests a wheelbarrow, a cradle, a girls' dress, 
and a boys' coat as well as a puzzle box, a "painted 
cube" test which involved the ability to visualize spatial 
relations, and a "plunger" test measuring speed and co- 
ordination of movement. In all but the two garment 
teat^the, ,,bpy s. pb taiued higher scores. It was also found 
that the boys' scores on the different spatial tests corre- 
lated more highly with each other and less highly with 
estimates of "general intelligence" than did the girls' 
scores. Frg>m this it was suggested that performance on 
such tests depends largely upon 
s* it is 

by s those processes which are included under the heading 
of "general intelligence." Tire method of arriving at a 
solution of the same problem might thus have differed 
for the two sexes. 


In another investigation (10) on English schoolchil- 
dren, 52 boys and 48 girls were given a series of tests se- 
lected from various current performance and non-language 
scales. 1 When scores on all the tests were lumped into 
a single measure and I.Q.'s computed from it, no signifi- 
cant sex difference was found, the average I.Q. of the 
boys being 96 and that of the girls 93. Analysis of per- 
formance on separate tests, however, revealed several 
marked sex differences. In ^general it was concluded 
that girls excel in tests of memory, learning, and non- 
form relationships, and boys excel in tests of 

geometrical form relationships and reasoning. 

Stenquist (43) reports that on his mechanical aptitude 
tests, elementary school girls obtained only about 65% 
as many correct items as boys, and that women in grad- 
uate school obtained about 80% as many correct items 
as unselected adult m,pn. In ,an extensive investigation 
conducted, with, the Minnesota Mechanical Aptitude Tests 
(37), similar differences were found. Seventh grade boys 
anXgirls, as well as male and female college sophomores, 
were employed in the sex comparisons. In Table XVII 
are shown the critical ratios (s^.tfaffference) f ^ e differences 
between male and female averages in each of these two 
populations. Sex differences were found in single tests 
as well as in Batteries A, B, C, and D. These bat- 
teries were composites of several tests, each test being 
weighted so as to yield the best possible estimate of 
mechanical aptitude. 

Those tests in which male superiority was most marked 
involved the use of mechanical materials which would 
be more common in the environment of boys. In block 
packing and card sorting, female superiority is usually 

1 Including Pintner-Paterson, Army Performance Scale, and Porteus maze 






(After Paterson, et at., 37, p. 274) 


Critical Ratios * 

Seventh Grade Pupils 

College Sophomores 

Minnesota Assembly 



Battery B 



Battery A 



Battery C 



Paper Form Board 



Battery D 



Minnesota Spatial Relations 



Packing Blocks 



Card Sorting 



* In this table a minus sign indicates a difference in favor of the girls. 

found. These tests involve chiefly visuo-motor coordina- 
tion with rapid shifts of attention, in which women 
generally excel (cf. above). 

In numerical aptitude a t .tendency towards male su- 
periority has likewise been found, although^are 

ao.t so consistent, as, m Jt&fi ...&$$ pf J^echanical aptkude. 

This also is to be expected from social tradition and en- 
vironmental conditions, since the sex differentiation in 
regard to mathematical work is not so pronounced as it is 
for mechanical pursuits. Girls are afforded relatively more 
opportunity for the development of mathematical abilities 
than for the exercise of mechanical functions. In the ele- 
mentary school, for example, girls are taught arithmetic 
in the same classes as boys, but the latter are still segre- 
grated for "shop courses." 

A few studies on the development of number concepts 
in p re-school children yield conflicting data (cf. 12). These 
studies are difficult to interpret on account of the relatively 


crude techniques employed, and also because of the close 
linkage between number concepts and language develop- 
ment in the young child. Test results on older subjects 
indicate a slight but fairly general male superiority in 
both, the mechanics of computation and mathematical 

An analysis of the data employed in the standardization 
of the Stanford-Binet showed that the average percentage 
of boys who succeeded on the numerical tests was greater 
than that of girls. The difference in favor of the boys was 
33% on the arithmetic reasoning test, 15% on the test 
of making change, and 10% on the "induction" test in 
which a generalized numerical rule must be discovered 
(46, p. 82). In an investigation on German schoolchildren 
(8), a continuous addition test was administered to 1214 
boys and girls in grades i to 8. In almost every grade, 
the boys completed more additions within the time allowed 
and made fewer errors than the girls. An extensive in- 
vestigation on various aspects of mathematical aptitude 
was conducted on 500 boys and girls in English secondary 
schools. The tests covered the following fields: arithmetic 
computation, arithmetic reasoning, mechanical algebraic 
processes, the use of algebraic symbols in problem solving, 
the manipulation of geometric constructs and spatial rela- 
tionships, and geometric reasoning. It will be noted that 
both mechanical and numerical abilities are involved in 
such tests. A small but consistent difference in favor of 
the boys was found on the series as a whole, larger and 
more significant differences being obtained on certain 
specific tests. 

Since 1930 a mathematical section has been added to 
the Scholastic Aptitude Tests administered by the College 
Entrance Examination Board to prospective college stu- 
dents (35). A large and significant sex difference in per- 


formance on this .part of the test has been found, as is 
illustrated by the 1930 results reported below. 

^ . Critical Ratio 
Boys Girls of D y ffrence 

Number of cases 4394 33 18 

Average score in mathematical 

section of Scholastic Aptitude 

Test 510-22 484-37 "-59 

It will be seen that the difference between the male and 
female averages is 11.59 times as l^arge as its standard 
error, which is far in excess of the minimum critical ratio 
of 3 required for perfect reliability. Similar results have 
been obtained in subsequent years. Itis interesting to note 
that this large and highly reliable difference ' was Build 
among subjects who had been exposed to the, differentiat- 
ing effects of environment over a considerable period 
of time, and that the corresponding differences among 
younger subjects were far less pronounced. 

In verbal or linguistic aptitude there is a fairly consistent 
difference "m '""favor "oTltTTemale'' sex. These differences 
"are manifested frbitr '"a"" Very early" age. 1 Observations on 
normaraTwell as ""gjftecf an'd feebleminded children have 
shown that on the average girls begin to talk earlier than 

boys. SroUsui^ a e k a ^ e ^,!f r er vo- 

cabulary than boys. In .one^^vestigation on 51 children 
at the age of 18 months, the average number of words 
employed by the girls was found to be 78.6 -and by the 
jDoys only 59. In another study the percentage of compre- 
hensible verbal responses was determined for each child. 
The average percentages proved to be 14 and 49 for boys 
at 1 8 and 24 months, respectively, as compared to 37 and 
78 for girls at the same ages. Speech defects ..and leading 

1 Cf. McCarthy (29) for a survey of sex differences in early language develop- 



disabilities are also less common among girls than among 
boys. Similar results have been obtained with all other 
indices of linguistic development (cf. 29, 52). 

Female superiority on linguistic tests persists through 
the successive academic levels. It is equally apparent 
among elementary schoolchildren and college students. 
Female superiority has been consistently reported in 
speed" of reading, naming opposites, and in all verbal 
association tests (53). Girls excel on sentence completion 
tests (12, 53)5 and a similar difference has been found in 
tests of story completion (53). On the verbal part of the 
Scholastic Aptitude Test, a large and highly reliable sex 
difference has been obtained in the reverse direction from 
that found in the numerical part (35). The average scores 
of the two sexes, as well as the number of cases in each 
group and the reliability of the difference, are shown 1 

. , Critical Ratio 

Boys Girls of Differgnce 

Number of cases 4394 3318 

Average score in verbal section 

of Scholastic Aptitude Test 486.98 5*7'54 X 3'5 2 

It is particularly significant that this reversal in the rela- 
, 5ver*stan3nig of the two sexes was obtained within the 
same group of subjects. It cannot therefore be attributed to 
selective 'factors or other spurious influences. 

Finally we may consider the results obtained in a large 
number of studies on memory. On practically all tests of 

*ur**. .***' 6***fc^^^ 

memory, a sex difference in favor of t$g ,1;^^].^ has-been 
found. As in the case of verbal ability, these differences 
have been observed very early in life and persist at all 
ages. There is considerable evidence to show female 
superiority in memory among pre-school children. Terman 
(45), in a study on 112 kindergarten children with the 


Stanford-Binet, found the girls superior on the tests of 
digit span and memory for sentences. Among the results 
obtained with the Stanford-Binet on older children, Ter- 
man reports girls superior in memory for digits and repro- 
duction of drawings from memory (46). 

In a number of studies (cf., e.g., 34, 40), girls have been 
found to excel more markedly in logical than in rote mem- 
ory. This is doubtlessly owing to the greater dependence 
of logical memory tests upon verbal comprehension. In a 
few cases in which the specific material of the test was 
more familiar or more interesting to boys, the relative 
standing of the two sexes was reversed. But these in- 
stances are very infrequent, and on the large majority of 
memory tests female superiority is found. This superiority 
has been established for a wide range of materials, for 
recall as well as recognition, and direct as well as incidental 
memory. In this connection mention may also be made 
of the fact that women have more vivid mental imagery 
than men in every sense modality. This finding, first sug- 
gested by Galton on the basis of his famous "breakfast 
table" questionnaire, has been subsequently corroborated 
by several investigators. 

Further data on sex differences in these various apti- 
tudes will be discussed in the following sections, in con- 
nection with intelligence test performance and records of 
scholastic achievement. The material on verbal and nu- 
merical aptitudes, in particular, needs to be largely sup- 
plemented from intelligence test results. Since these 
abilities have not been generally recognized as distinct 
from "general intelligence," there are relatively few stud- 
ies on sex differences in verbal or numerical abilities as such. 

In reference tp the possible origin of sex differences in 
special aptitudes, a comment offered by Burt several years 
ago is of interest. He states: 


Sheltered, supervised, detained at home, girls . . . incline 
to sedentary lives and engage in literary pursuits; and . . . 
they consequently excel in linguistic work and conversational 
activities. Boys . . . have more to do with practical, per- 
ceptual, out-of-door pursuits. They are sent to shops with 
money. They are allowed to play and wander in the streets. 
They are encouraged to handle tools to construct toys for 
amusement and articles for use. No wonder that . . . boys 
grow more ready with hand and eye than with tongue or 
pen (5, p. 196). 


On the Binet test and its revisions., sex differences are 
sligEFBuf usually favor the girls up to the age of about 14. 
Terman (44) reports results obtained with the Stanford- 
Binet on 457 boys and 448 girls between the ages of 5 and 
14. The average I.Q. of the girls was found to be higher 
than that of the boys at every age except 10, at which they 
were equal, and at 14, at which the boys excelled. The 
specific data for each age group are reproduced below. 

Age Boys Girls 

5 ioo 104 

6 99 105 

7 101 103 

8 IOO IO2 

9 98 102 

10 103 103 

11 96 101 

12 97 99 

13 96 97 

14 ioo 96 

These differences, although slight, are consisferit .iyith 
the findings of other investigators, Burt (5) tested 3500 
London schoolchildren, ranging in age from 3 to 14, with 
his own revision of the Binet tests. With the exception of 
a single age group, the girls obtained higher average mental 


ages than the boys. In general this difference amounted to 
about -j- of a year. Goodenough (13) administered the 
Kuhlman-Binet to 50 boys and 50 girls at each of the ages 
2,- 3, and 4. The average I.Q. of the girls was again higher 
than that of the boys, this difference persisting when the 
children were retested after a lapse of six weeks. Thus the 
oBtained difference could not be attributed to chance 
fluctuations or a response to novel situations. 

With most group tests, a similar female superiority up 
to the age of 14 has been found. Thus in several extensive 
school surveys with the National Intelligence Test, girls 
have obtained consistently higher scores than boys (cf., 
e.g., 54). On the Dearborn group scale, which is less de- 
pendent on verbal ability than most group scales, however, no 
consistent sex difference was found in a group of 3400 
children between the ages of 7 and 17 (cf. 25). 

Among high schqol .students, on the other hand, boys 
generally excel on intelligence tests. 'Tharndfelso), using 
a group mtelligenc^.^q.ak, especially , .constructed for the 
high school level, with about 2500 high school students 
between the ages of 13 and 18, found the boys to be 
superior on the average. Similarly, in an investigation on 
1453 high school students with the South Dakota Group 
Intelligence Test, 1 boys were found to excel, their superior- 
ity increasing from the first to, the last, year, of. high school 
(3). In a number of studies employing the Army Alpha 
with both high school and college groups, consistent male 
superiority was also found (cf., e.g., 55). 

These sex differences in total scores on intelligence tests 
can be explained in terms of certain previously reported 
findings. The^^en^^ age 

on the Binet tests, as well as on most ofjthe groi^p tests, 

3 Including tests of directions, analogies, synonym-antonym, reading com- 
prehension, information, and arithmetic. 


is to be expected on the basis of the large verbal content of 
such scales and their frequent use of memory tests. It will 
be recalled that girls excel in both of these aptitudes. This 
interpretation of female superiority in general intelligence 
tests is supported by the fact that the sex difference dis- 
appears or becomes reversed when tests like the Dearborn, 
which lay less emphasis upon verbal ability, are employed. 
The consistent male superiority on Army Alpha has like- 
wise been attributed to the fact that this scale was orig- 
inally standardized on men and thus may contain an ex- 
cess of items which favor men. FiagHy,, the reversal 9$ ^ e 
relative status of the two sexes in high school groups has 
already been explained in terms of selective factors (cf. 
Ch. XIV). Even when predominantly verbal tests are 
employed, male superiority is found among high school 
students. The fact that this superiority of the boys f tends 
to increase throughout the four years of high school fur- 
ther corroborates the proposed, explanation. 

That sex differences on tests of so-called general intelli- 
gence are attributable to differences in special aptitudes is 
also indicated by an analysis of scores on the separate 
subtests of intelligence scales. Thus an examination of the 
scores obtained by 834 high school students on Army 
Alpha showed male superiority only on the arithmetic 
reasoning, number series completion, and information 
tests (55). The differences on these tests were sufficient to 
pull up the total scores and produce a sex difference in 
favor of the boys on the scale as a whole. 

In a previously mentioned investigation with the Pres- 
sey Group Test (cf. Ch. XIV), the scores of 880 children 
between the ages of 9 and 14 were examined with reference 
to performance on each of the ten subtests of the scale. 
It will be recalled that at these ages the girls excelled in 
total score. On the separate tests, however, the boys 


excelled in arithmetic at all ages and in practical informa- 
tion from age n on. The girls excelled in rote memory for 
words, naming opposites, word completion, dissected sen- 
tences, analogies, and moral classification, the last depend- 
ing largely upon verbal comprehension. In the remaining 
two tests, no significant sex difference was exhibited (39). 
It will be recalled that among high school seniors, owing 
to a differential elimination of male and female students, 
boys excelled in total scores on the Pressey test (4). Per- 
formance on the separate tests, however, showed the same 
hierarchy as in the younger groups. Thus the boys ex- 
celled markedly in the arithmetic and information tests. 
The girls obtained higher average scores in word com- 
pletion, dissected sentences, and logical memory. On the 
remaining tests there was either no difference or a slight 
superiority of the boys. The reversal in total score from 
the elementary to the high school groups results from the 
fact that the high school senior boys excelled by a much 
larger amount in those same tests in which elementary 
school boys excelled. Similarly, the high school senior 
girls excelled by a smaller amount in the tests in which the 
elementary school girls had excelled markedly. 


On the whole gMsjexcsi JjL^2!^./Ag/Arrf^. achieve- 
ment, as revealed botkiy achievement .test records aiiyd by 
school grades. Performance on the separate parts 
ardized achievement , tests y however,- shows , a, JbLi 
abilities in different school subjects, which corresponds 
closely to that found with tests of, iiitjp,llige:nce w aiid- special 
aptitudes. In an investigation (8) on 300 schoolchildren 
with the StanfbKTlKffi^ sex (difference was 

"fouiid in total achievement "quotient But an analysis of 
the scores indicated a definite superiority of the, .girls in 


reading, .language. .usage, and dictation, and of the boys 
in arithmetic, nature study, and history. In another 
investigation (51) a standard geometry test was admin- 
istered to 410 high school boys and 349 high school girls, 
all of whom had previously been given the Terman Group 
Test of Intelligence. The boys as a group were found to 
excel in geometric ability when compared with girls of equal 
"intelligence" as indicated by the Terman scores. 

Numerous other extensive school surveys have yielded 
the same general results. 1 In general girls obtain higher 
achievement test scores in subjects requiring verbal abil- 
ity or memory. Boys excel, in those subjects which call 
into play numerical or spatial aptitudes, as well as in cer- 
tain "information" subjects such as history, geography, 
and general science. This is in agreement with the common 
superiority of boys on tests of general information, and 
probably results from the less restricted and more hetero- 
geneous environment to which boys are exposed as well 
as from their wider range of reading interests. Thus Ter- 
man (47), in his survey of the reading habits of gifted 
children, reports that the girls read imaginative and emo- 
tional fiction as well as stories of school and home life far 
more often than the boys, while the latter showed a pre- 
dominant interest in books on science, history, biography, 
travel, and informational fiction and adventure tales. 

In regard to school progress, girls are consistently more 
successful ""tTiaa Boys. The differences, although small, 
appear irrespective of the particular criterion of school 
progress employed. Girls are less frequently retarded, 
more frequently accelerated, and promoted in larger num- 
bers than boys. Typical results from a survey conducted 
in the schools of 318 cities are shown in Table XVIII. 
Since girls make more rapid progress than boys in school 

1 Cf. Lincoln (26), Ch. IV, for a survey of this material previous to 1927. 



promotions and since most comparisons of achievement 
are made on the basis of school grade, it follows that age 
comparisons would show an even greater superiority of 

In school grades girls excel consistently even in those 
subjects which favor boys. Thus a comparison of grades in 
arithmetic, or history, or any "other subject in which boys 
obtaiiTKigKer achievement test scores, shows a sex differ- 
encelh favor of girls. The advantage enjoyed by girls in 
school grades was made particularly vivid in an investiga- 
tion (25) on 202 boys and 188 girls in grades 2 to 6, all of 
whom were given the Stanford Achievement test. The 
girls were found to excel consistently in school grades, 
when compared with their achievement test scores. Thus the 
grades showed a far greater female superiority than seemed 
to be warranted by performance on objective achievement 




(After Lincoln, 26, p. 100) 

School Status 

Cities of over 25,000 

Cities of less than 










I year over age 





2 years over age 





3 years over age 





4 years over age 





Total over age 





Total under age 





v., high school girls generally obtain better 
grades than high school boys, even though the latter are 


a more select group and make a ^better $ ho wing,, o,a in- 
telligence tests (cf. 36). This is illustrated by, a survey of 
the^grades^given to students in each of the four years of a 
single high school, the results of which are shown in 
Table. XIX. It will be noted that in each year, without a 
single exception, the percentage of A's and B's is larger 
and the percentage of D's and F's is smaller among the 
girls than among the boys. The larger percentage of boys 
than girls who left school further suggests the better ad- 
justment of girls to the school situation. 




(After Lincoln, 26, p. 93) 


First Year 

Second Year 

Third Year 

Fourth Year 






































21. 1 






I6. S 



I8. 3 







Left school 









Various explanations have been offered for the greater 
scholastic success of girls. Among the, i( 3^ajp.j^faiKti5wnay 
be mentioned girls' dem9nstra^^ 

altitude, whi<& prqbablyplays an in^port^xjJjjjL^ij^^jxlj^ 
all school subjects. Current methods of instruction, as 
well as methods of testing, are predominantly verbal. The 
child who expresses himself well, furthermore, will impress 
the teacher as being relatively brighter than one who is 
linguistically backward, and this may in turn affect their 
respective grades. A second possible factorjn^jthe^higher 
lastic ratings of ^girl?TF : Sie^li^tness and general su- 

"*--*- _.. L ^^**Q - i**^ J *awi ! -wm t ^^, v ^ w ,^,^ 1 . ,.*. 



periority of their handwriting. In most investigations on 
both elementary and high school groups, girls have been 
found to excel markedly in the quality of their handwrit- 
ing, as judged by standardized product scales (cf. 26, 

pp. 72-77)- 

Finally owing to the obvious presence of a subjective 
element in school grades, personality differences between 
boys and girls may influence the allotment of such grades. 
Girls are generally more docile, quieter, less resistant to 
school discipline, and are less often "behavior problems" 
than boys. This difference in the child's attitude towards 
school affects his grades both through the amount of ma- 
terial actually learned and, more directly, through the 
general impression created on the teacher. 


That definite personality differences exist between adult 
men and women in our society is clearly apparent from 
everyday observation. In many emotional and social 
characteristics, this differentiation is noticeable from an 
early age. An important aspect of personality develop- 
ment in which traditional sex differences are manifested 
includes interests, preferences, ideals, attitudes, and per- 
sonal sense of values. These characteristics, because of 
their relatively subtle and persistent nature, often exert 
an unsuspected influence, not only upon the development 
of emotional and character traits, but also upon the in- 
dividual's achievements and effective abilities. An in- 
teresting observation recorded by Thompson (49) illus- 
trates this effect. In discussing the superior performance 
of a group of men as contrasted to a group of women 
on a problem of mechanical ingenuity, she wrote: 

It is very difficult to evaluate this difference because of 
the indefinite nature of the problem. Most of the women 


expressed a great distaste for all such problems, because they 
were uninteresting. Many of them were so uninterested that 
they did not really work at it. Whether the men found it 
equally uninteresting, but forced themselves to work in spite 
of lack of interest, or whether the problem appealed to them 
as more interesting, it is difficult to say. From the voluntary 
comments of the subjects the latter hypothesis seems more 
probable (49, p. 116). 

It has proved quite difficult to obtain objective or 
quantiB;tfv^M*<S'asttfes of these characteristics. A number 

j^ ^ ^^ differences employed 

the free association technique, whereby the subject is 
presented with a list of stimulus-words and is required to 
respond by giving the first word suggested to him by each 
stimulus-word. Although admittedly crude, these early 
experiments yielded fairly consistent results which were 
also in general agreement with common observation. 1 In 
general women's associations seemed to indicate an in- 
tefestTTrT tfie immediate surroundings, finished products, 
the ornamental, the individual, and the concrete, whereas 
men's associations suggested an interest in the more re- 
mote, constructive, useful, general, and abstract. Dynamic 
concepts were more common among the men's responses, 
static among those of the women. Time was more prom- 
inent in the men's associations, space in the women's. 
The free association responses of women also tended to 
be more subjective, personal or particular, social, and 
emotionally toned than those of men. 

Equally characteristic and traditional ^differeace^ were 
revealed in a large number of subsequent studies on, qhil- 
dren. Sex differences were investigated through an analysis 
of literary and reading preferences, spontaneous con- 
structions and drawing choices, aesthetic preferences, 

1 For a survey of these studies, see Miles and Terman (32). 


vocational choices, and choice of ideals. Thus in one 
typical investigation (21), 200 schoolchildren were re- 
quired to rank nine pictures, each representing a specific 
type of appeal, in order of merit. The chief sex difference 
noted was the relatively high position assigned by girls 
to pictures dealing with children, and by boys to those 
whose main theme was action and the heroic. 

A series of more recent studies have approached the 
same problem through an analysis of conversations. In the 
first of these investigations (33), a record was made of 
conversations heard in the evening along a busy thorough- 
fare in the heart of New York City's theatre district. 
When the participants were classified according to sex, 
it was found that the most frequent topics of conversation 
among women were clothes and social affairs, and among 
men, money and business affairs. In conversations between 
men and women, there was a predominance of men's conver- 
sational topics, which suggested a tendency for women to 
adapt themselves to the interests of their male companions. 

In a subsequent study (24), conversations were collected 
in a wider variety of situations in a mid-western city. 
Observations were made on a college campus, in barber 
shops, churches, hotel lobbies, street cars, and other public 
or semi-public places. Although typical conversational 
differences were noted from one locale to another, the 
general results corroborated those of the New York study. 
The two major topics in order of their frequency were, 
among women, (i) men and (2) clothes; and among men, 
(i) business and money, and (2) sports and amusements! 
It is also interesting to note that " people" of either sex 
played a larger part in the conversations of women than 
in those of men, having been observed in 37% of the 
former and only 16% of the latter. A similar series of 
observations was made in two London streets (23). The 


results resembled closely those of the American studies, 
with two major exceptions. First, in all conversations 
business and money were less prominent, and secondly, 
in conversations between men and women there seemed 
to be a greater tendency for the men to adapt to women's 
interests than in the American groups. 

Qonsistent sex differences have also been reported in 
th<e individual's conception of values. The application of 








Men (N=463) 
Women (N*313) 




Theoretical Economic Aesthetic Social Political Religious 

Type of Value 

ALLPORT-VERNON STUDY OF VALUES. (Data from Allport and Vernon, 2, 
p. 246.) 

the Allport-Vernon "Study of Values" (2) has furnished 
some information on these differences. This is a test of 
the questionnaire type, in which each response is given a 
numerical weight in one of six sets of values, viz., the- 
oretical, economic, aesthetic, social, political, and religious. 
The relative standing of the subject in each set is then 
determined by totaling scores on separate items, and a 
psychograph is constructed -from these six measures, 
Psychographs showing the average scores of 463 men and 
313 women will be found in Figure 48. It will be noted 


that among the women the highest average values fall 
in the esthetic, social., and religious groups, in the order 
given, while among the men they fall in the theoretical, 
economic, and political. 

In connection with the higher rating of social values 
among women, mention may be made of the widely quoted 
female superiority in social perception. Relatively little 
information is available on this point, but a comparison 
of the performance of men and women on the George 
Washington Social Intelligence Test may prove relevant. 
In a group of 430 college students of both sexes who took 
this test, a small difference in total score was found in 
favor of the women (20). The average scores obtained by 
freshmen and upperclassmen of each sex were as follows: 

Freshmen Upperclassmen 

Men 101 109 

Women 108 115 

Upon analysis, this difference was found to be owing al- 
most entirely to the higher scores of the women students 
on two subtests. One of these was designed to measure 
the ability to decide the "best thing to do" in a difficult 
social situation. The other involved a knowledge of com- 
mon facts of human behavior which could be acquired 
through the everyday observation of people* In view 
of the larger part played by women in social situations 
and the more frequent concern of women with the reac- 
tions of others, such differences are easily understand- 


Those aspects of personality commonly .designated as 
moral of character traits also present Atypical ^differences 
between the sexes. In an investigation (42) on tnoraT 


judgment, a list of 100 acts, including commendable as 
well as reprehensible activities all of which might be car- 
ried out by a young man of 18, were to be rated on a scale 
ranging from 10 to +10. The, subjects were college 
students, 39 men and 39 women. Analysis ,ql responses 
showed that the relative ratings given to each act by men 
an3~women were very similar, i.e., the same acts were 
cEosen as Best and worst by both sexes. There was, how- 
ever, a tendency for women to assign more extreme ratings 
both to good and to bad acts. The men gave more medi- 
ocre or indifferent ratings, while the women employed 
more frequently the values towards the 10 and +10 
ends of the scale. Although the procedure was crude and 
the number of cases small, these findings are suggestive. 
The tendency of the female group to be more critical, 
both favorably and unfavorably, is in line with the tradi- 
tional belief that women are the custodians of the social 
mores, as well as with the common practice of attaching a 
greater ethical or moral significance to the activities of 
women than to those of men. 

In an extensive series of tests by^HartsljLQjcne, ,May, and 
Shuttleworth (16) , on approximately 85o_xkmejQitary 
schoolchildren in three cities, reliable differences in. favor 

olths gl4s,were, r fouBdiJl ,mQ^l, Jk^Qwledga,, 

attitudes. Several tests of each of these aspects of char- 
acter development were employed. In order to keep as 
close as possible to the children's own opinion, the tests 
were worked up in the form of ballots and the children 
were asked to "vote" on each item. In the so-called 
"duties test," for example, several propositions were 
given with the request that the subject indicate whether 
it is his duty to do these things, by underlining Yes, No, 
or S (sometimes yes and sometimes no). Some of the 
items in this test were as follows (16, pp. 46-47): 


1. To help a slow or dull child with his lessons Yes S No 

2. To call your teacher's attention to the fact if you 

received a higher grade than you deserved Yes S No 

3 . To smile when things go wrong Yes S No 

4. To report another pupil if you see him cheating Yes S No 

In total scores on both the moral judgment and social 
attitudes tests, the differences in favor of the girls were 
4.31 times as large as their standard errors and can there- 
fore be regarded as perfectly reliable. The investigators 
conclude that: "It appears on the surface at least th#t 
girlFlireTnore sensitive to both conventional and ideal 
social standards than boys" (16, p, 119). 

Certain significant sex differences have alfco been dis- 
covered in objective behavioral tests of character. In a 
series of investigations by Hartshorne and May (14, 15), 
tests were devised for the measurement of "deceit? in- 
cluding cheating, lying, and stealing, "service" including 
cooperative and charitable behavior, and "self-control," 
including persistence and inhibition. Among the special 
advantages of these tests may be mentioned the fact that 
the subjects did not realize that they were being tested 
or that their actions could be detected. All observations, 
furthermore, were made in the course of ordinary every- 
.day activities of the children, including school work, home- 
work assignments, athletics, and party games. Data on de- 
ceit were collected on some 10,865 elementary school pupils 
in several parts of the country. For the main studies on 
service and self-control, about 900 children were employed. 

No consistent sex difference in deceptive .behayigj was 
4isQYered. Analysis* of "separate tests showed that: "On 
some tests the girls are more dishonest, whereas on others 
the boys show the greater tendency to deceive" (14, 
p. 1 68) . InjgiftjLjiAlys^. of $ewfc&<wd~^^ com- 

were made,bpt;h in test scores 


among classmates and teachers. The final summary data 
on sex differences in these traits are shown below (cf. 15, 
pp. 156, 380, 382): 

Difference n . . . n ._ 
*?_._ _ . Direction of Difference 

S.E. of Difference 

Total service scores 1.9 Girls more cooperative 

Reputation for service 7.9 Girls more cooperative 

Total persistence scores 1.7 Girls more persistent 

Reputation for persistence 7.6 Girls more persistent 

Total inhibition score 5.5 Girls better inhibited 

Reputation for inhibition 5.0 Girls better inhibited 

It will be noted that all of the above differences are in 
favor of the girls. In service and persistence, however, 
the differences in total score are not reliable. The relative 
standing of the two sexes also varied from test to test. 
In inhibition, on the other hand, the girls were reliably 
superior in total score and consistently superior on each 
individual test. The more successful adjustment of girls 
to the school situation may be owing partly to these per- 
sonality differences. It is also interesting to note in this con- 
nection that in reputation the girls excel the boys markedly 
in all traits. This too may influence their school success. 

The discrepancy between reputation and performance 
is J^$^f interest In relation to socialpressure. Kiia^rbe 
that with increasing age the cumulative force of social- 
expectancy becomes more effective and the discrepancy 
between behavior and traditional belief is les&enedu With 
this would come an increasing differentiation between the 
sexes. Until similar behavior tests are made on adult 
subjects, these questions cannot be answered. 


In general emotional adjustment and nature of emo- 
tional response, our cultural tradition has taught us to 


expect pronounced differences between man and woman. 
The recent development of standardized personality tests 
and their application to college groups have revealed a 
number of significant sex differences. The belief in the 
greater emotional instability of the female has been re- 
flected in test scores. Thus the responses of about 600 
male and 400 female college students on one of the Col- 
gate Mental Hygiene Tests (22) indicated an average of 
20% more psychasthenic symptoms among women. 

In an investigation on introversion (17), 100 college 
men and 100 college women rated themselves and were 
also rated individually by two associates on 54 typical 
introvert traits. No significant sex difference was found 
in introversion-extroversion, the average scores of men 
and women" beihg^ It. 41 arid 11.12, respectively. But 
further analysis of responses showed a sex difference in 
another trait which cut across introversion-extroversion 
ani&eemecl to bear no relation to it. This trait is concerned 
predominantly with social relations. The introvert traits 
marked most often by men were those which would in,ter- 
fer v e with social adjustments. Those marked most often 
by women, on the other hand, were such as to interfere 
with efficient work. A few examples will illustrate this 

Typical "masculine" symptoms of introversion: 

1. Outspoken 

2. Works things out on own hook; hesitates to accept help 

3. Keeps in background on social occasions 

4. Conservative and painstaking in dress 

5. Introspective 

Typical "feminine" symptoms of introversion: 

1. Shrinks when facing a crisis 

2. Works by fits and starts 

3. Has ups and downs in mood without apparent cause 

4. Feels hurt readily 

5. Hesitates in making decisions on ordinary matters 


Comparisons of male and female college students have 
also been made on the Bernreuter Personality Inventory. 
This test, consisting of 125 questions, can be scored with 
six different keys for as many different traits. 1 The 
average scores obtained by male and female college groups, 
as well as the critical ratios 2 of the differences, are shown 
below. The number of cases in these groups varied from 
144 to 658. 



Average Score 
Male Female 

S.E. of Difference 

Direction of 

BiN: Neuroti- -57.3 -42.8 

Women more 
neurotic, or 

Men more self- 

Women more 

Men more 

Men more self- 

Women more 
and socially 

In all but .the sociability scale, the sex differences are 
perfectly reliable. This trait may include more than one 

1 The fact that some of these traits have recently been shown to be mutually 
interdependent introduces unnecessary duplication in the scores but in no way 
vitiates the comparisons made. All six scores are 'reported here for the sake of 

2 Computed by the writer from Bernreuter's published data see manual of 
directions and norms, October, 1934. 

B 2 S: Self- 


Bsl : Introver- 

B 4 D: Dom- 

FiC: Con- 

F2S: -Socia- 

27-o 6.8 

-25.6 -14.7 

45-9 30.6 

-51-5 8.7 

-25-9 --3I-I 








counteracting factor in which the sexes might differ sig- 
nificantly. In introversion, it will be noted that women 
obtain significantly higher average scores. This seems to 
conflict with the findings reported above. The explanation 
of this discrepancy may lie in the particular choice of 
items in the two tests. Thus Bernreuter's test may be 
overweighted with the more "feminine" type of introvert 
items. In all studies on personality, it is difficult to gen- 
eralize regarding trait differences because of the specificity 
of responses. The sex differences in confidence and self- 
sufficiency on the Bernreuter test are particularly large. 
The differences in dominance and neuroticism are clearly 
reliable, but smaller. It should be kept in mind, of course, 
that these data apply only to college students, A differed 
picture might be presented by other adult groups. It is 
unlikely, however, that the sex differences in non-college 
groups should be smaller, since the environment of college 
students is probably more uniform than that of other 
male and female adults in our society. 

Interesting comparative data on the emotional differ- 
ences between boys and girls at successive ages have been 
obtained with the Woodworth-Mathews questionnaire 
(28). This is an adaptation of the Woodworth psycho- 
neurotic inventory for use on children. It consists of 
100 questions dealing with the following classes of 
symptoms : 

1. Fears, worries, perseverations 

2. Physical symptoms, such as muscular twitchings 

3. Unhappiness, anti-social moods 

4. Dreams, phantasies, sleep disturbances 

This test was administered to 575 boys and 558 girls be- 
tween the ages of 9 and 19. The median number of neu- 
rotic symptoms reported by the boys was 20, and by the 


girls 25.5. This sex difference is in agreement with the 
findings on adults. But an analysis of scores in different 
age groups brought out certain rather suggestive facts. 
The changes in score with age among boys and girls are 
shown graphically in Figure 49. 

It will be seen that at age 10 the median number of 
symptoms reported by the boys is greater than that re- 




Z. 20 



10 11 12 13 


15 16 17 18 

28, p. 21.) 

ported by the girls. At u there is no appreciable sex dif- 
ference, and beyond this the girls show an increase in 
emotional instability and the boys a decrease. This, to be 
sure, is what would be expected from an analysis of the 
environments of the two sexes. The emotional problems 
and affective milieux of boys and girls are quite similar in 
early childhood. Gradually, however, the environmental 
differentiation becomes pronounced and this is reflected 
in the increasing divergence of the sexes in emotional 


A very compr^^ to the problem of 

differences in personality traits has recently been made 

,(,.,, ... ***- .1 **!,. .,,,.', ,-^/f !-, ^ .',/<. ; f .-<> "<-V < ',,;,,! ., : - ,->,.,. , .', < '!.;,:*/' 


by Terman and Miles (46). The aim of this investigation 
was to devise a scale which would differentiate clearly 
between the characteristic male and female patterns of 
response. After an exhaustive survey of the literature 
and prolonged research, items were selected which re- 
vealed the most pronounced differences between repre- 
sentative samplings of the two sexes in our society. Data 
were collected on many hundreds of subjects, including 
elementary, high school, college, and graduate students, 
unselected adults, members of several occupations, and 
specially selected groups such as athletes, juvenile delin- 
quents, and adult homosexuals. 

Seven tests were included in the final scale. The first 
is a word association test and the second an ink-blot asso- 
ciation test. In both tests the response is of the multiple 
choice form, the alternatives under each item including 
distinctly masculine as well as distinctly feminine re- 
sponses. An information test, drawing upon a wide variety 
of fields, is likewise of the multiple choice variety. In a 
test of emotional and ethical response, the subject is re- 
quired to check the degree to which a given situation pro- 
vokes in him emotions of anger, fear, disgust, or pity; in 
the second part of this test, the degree of moral seriousness 
of each given type of behavior is to be indicated by check- 
ing 3, 2, I, or o. An interest test follows, in which the sub- 
ject expresses his liking, disliking, or indifference towards 
a wide range of items, including occupations, people, 
games and amusements, movies, magazines, school studies, 
books and literary characters, travel and sightseeing pref- 
erences, and special interests. The sixth is a test of opin- 
ions^ in which a series of common beliefs and superstitions 
are to be marked true or false. The last is a test of in- 
trovertive response^ the items having been selected from 
several current scales of introversion-extroversion. A 


composite weighted score on all seven tests can be ob- 
tained for each subject. 

This scale proved very successful in differentiating 
between the responses of male and female groups. All 
sex differences in average score were statistically reliable, 
the smallest being 3.4 times as large as its standard error. 
An intensive analysis of the characteristic male and fe- 
male responses on each test revealed a distinct picture of 
the "temperaments" of the two sexes in our culture. 
Terman and Miles summarize these differences as follows: 

From whatever angle we have examined them the males 
included in the standardization groups evinced a distinctive 
interest in exploit and adventure, in outdoor and physically 
strenuous occupations, in machinery and tools, in science, 
physical phenomena, and inventions; and, from rather occa- 
sional evidence, in business and commerce. On the other 
hand, the females of our groups have evinced a distinctive 
interest in domestic affairs and in aesthetic objects and oc- 
cupations; they have distinctly preferred more sedentary 
and indoor occupations, and occupations more directly min- 
istrative, particularly to the young, the helpless, the dis- 
tressed. Supporting and supplementing these are the more 
subjective differences those in emotional disposition and 
direction. The males directly or indirectly manifest the greater 
self-assertion and aggressiveness; they express more hardi- 
hood and fearlessness, and more roughness of manners, lan- 
guage, and sentiments. The females express themselves as more 
compassionate and sympathetic, more timid, more fastidious, 
and aesthetically sensitive, more emotional in general (or 
at least more expressive of the four emotions considered), 
severer moralists, yet admit in themselves weaknesses in 
emotional control and (less noticeably) in physique (46, 
pp. 447-448). 

In regard to the origin of such differences, the authors 
offer only tentative hypotheses. The role of cultural 


factors is, however, constantly admitted throughout their 
discussion. Several lines of evidence are cited which sug- 
gest the importance of nurture in the development of 
whatln^our society is regarded as a typically "masculine" 
or "feminine" personality. Thus the masculinity-fem- 
ininity index was found to be associated with amount of 
education, occupation, and domestic milieu. Such 
factors as the death of one parent, excessive or exclusive 
association with one or another parent, and predominance 
of brothers or sisters among the siblings, were much more 
closely linked with masculinity-femininity scores than 
were physical traits. Highly intelligent and well-educated 
women tended to score more " masculine" than their sex 
norms. Similarly, " cultured" men, i.e., men who had 
cultivated avocational interests of an artistic or intellec- 
tual sort, tended to test more "feminine." Thus the 
equalizing influence of specific training or experience in 
the two cases seemed to bring about a convergence of 
the temperamental qualities of the two sexes. 


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The comparative evaluation of the races of man has 
long been a subject of keen interest and lively controversy. 
It is an interesting commentary upon human thought 
that nearly all theories of racial inequality proclaim the 
superiority of the particular race of their respective ex- 
ponents. Thus Aristotle (cf. I, pp. 318-320) endeavored 
to demonstrate that the intellectual leadership of the 
Greeks must of necessity follow from their favorable 
geographical location. He argued that the peoples in- 
habiting the colder regions of northern Europe, although 
outstanding for bravery and physical prowess, were in- 
tellectually incapable of a high degree of political organiza- 
tion or leadership. Similarly, the Asiatics, although in- 
tellectually keen and inventive, 'lacked spirit. The Greeks 
alone, being geographically intermediate, were endowed 
with the proper balance of these traits and were thus by 
nature fitted to rule the earth. Similar claims have been 
made for such groups as the Arabians, the Romans, the 
French, the Anglo-Saxon, the "White" race as distin- 
guished from those having a different skin pigmentation, 
the Nordics, the Alpines, the Mediterraneans, and various 

Outstanding among such theories, because of its wide- 
spread popularization, is that proposed by de Gobineau 
(10) in the nineteenth century and subsequently expanded 
by Chamberlain (7). This doctrine had numerous followers 
who reformulated it and developed it along various lines. 


Its basic contention, however, is the superiority of 
the Nordic or "Aryan" race, a loosely and ambiguously 
defined group whose descendants are now supposed to 
inhabit for the most part the countries of northern 
Europe. The array of evidence cited in support of this 
theory is incomplete and one-sided at its best and fantastic 
and mythical at its worst. The concepts involved in 
such a theory will be critically examined in the course of 
the subsequent discussion. 

At present, race problems are a particularly lively issue. 
Outworn and forgotten theories are being revived in the 
attempt to rationalize political actions and policies. Under 
the stress of emotional appeal, it is especially difficult 
to carry on unbiased and objective analysis of facts. It 
is one of the earmarks of prejudice to draw logically un- 
warranted inferences from the data at hand. In a current 
test (34) for the measurement of the prejudice-fairminded- 
ness variable, for example, one of the subtests is based on 
just such behavior. The subject is given certain facts 
bearing upon controversial issues, with the instructions 
to check any of the proposed conclusions which seem to 
him to follow directly from the given data, regardless of 
their truth or falsity in general. The individual who is 
biased or who responds emotionally to any of the issues 
involved will ignore the limitations of the facts actually 
presented and will generalize far beyond them. The pro- 
cedure in this test presents a close parallel to what proba- 
bly occurs all too often in the interpretation of data on 
such emotionally toned issues as race differences. 

Under such conditions it is essential to emphasize and 
to bear clearly in mind the possible vitiating factors and 
sources of error in the data. As in all group comparisons, 
studies on race differences must take into account selective 
factors and adequacy of sampling, overlapping of dis- 


tributions, reliability of an obtained difference, inaccuracy 
or ambiguity of the measuring instrument, and other 
similar factors which have already been discussed and 
illustrated (cf. Ch. XIV). It is probably not an exaggera- 
tion to state that failure to consider such factors has in- 
validated the large majority of investigations which pur- 
port to have established a racial difference in one or 
another behavioral trait. 

Racial comparisons are an extremely difficult problem 
of differential psychology. In addition to the above- 
mentioned sources of error which they share with all 
group comparisons, studies on race differences are handi- 
capped by special difficulties inherent in every phase of 
the problem. Thus it has proved a difficult matter in 
such studies to decide whom to measure, what to measure, 
and how to measure it. These difficulties will be analyzed 
in the present and subsequent chapter. The first of these 
two chapters will be concerned with questions of whom 
to measure, or the selection and classification of subjects 
in racial studies. In the second chapter will be discussed 
some of the major problems which arise in the efforts to 
measure and compare widely diverse groups. 

The data of investigations on race differences have been 
grouped about these methodological questions. No gen- 
eral summary of findings or intellectual hierarchy of racial 
groups is presented because, although apparently useful 
as a mnemonic device, such a tabulation would be highly 
misleading and of very dubious value. Isolated facts are 
particularly misleading in racial comparisons and should 
at all times be evaluated in terms of the conditions under 
which they were collected. Conclusions on race differences 
will therefore be drawn only in the light of a critical analysis 
of the entire problem and will not be divorced from their 
limiting conditions. No attempt has been made, further- 


more, to survey the vast array of investigations on psy- 
chological differences among racial groups. For summaries 
and more extensive discussions of this problem, the reader 
is referred to a review (14) and book (16) by Garth and 
to the more recent and very stimulating book by Klineberg 
(24). For an orientation into the general problem of race, 
books on anthropology, such as those of Boas (4) and 
Kroeber (26), may be consulted. 


Tradition, prejudice, and the snap judgments of every- 
day observation have contributed to the development of 
a concept of race as a clearly differentiated and easily 
identifiable group, possessing distinctive physical, mental, 
and temperamental characteristics. The observations of 
biologists, anthropologists, and psychologists, however, 
fail to support such a view. 1 The classification into racial 
groups is essentially a biological one and corresponds to 
such divisions as breed, stock, and strain in infrahuman 
organisms. In its simplest terms, any definition of race 
implies, a certain .community of physical characteristics based 
pnm^nly up&ik $ common heredity,, 

The task of race classification is far more complex than 
would appear from the glibness with which individuals 
are commonly assigned to one group or another. The 
five-fold classification of races memorized by every school- 
child is of historical interest only. This division can be 
traced to Linnseus (27), the great classifier, who recog- 
nized four races of men Europeans albus (white), Ameri- 
canus rubescens (red), Asiaticus fuscus (yellow), and 
Africans* niger (black). A fifth group, the brown race, 
was subsequently added by Blumenbach (2), who also 

1 For a very readable account of many of the difficulties of race classification, 
see Huxley and Haddon (21). 


altered the terminology, proposing the now familiar classi- 
fication into Caucasian, Mongolian, American, Ethiopian, 
and Malayan. This classification is crude and superficial, 
as will shortly become apparent. 

The essential problem in the classification of racial 
groups consists in the identification, of inheritable physical 
characteristics which differ clearly from one group to 
, aootKer End which may thus serve as criteria^ jace. A 
wide variety of such criteria have been proposed and 
applied (cf. e.g., 24, 26). Skin color is popularly .employed 
as one of the most obvious means of racial identification. 
In spite of its widespread use, however, it has proved 
to be one of the least satisfactory of the possible criteria. 
It is a well-established fact that the same pigments are 
present in all human skins and that different skin colors 
result from varying relative amounts of each pigment. 
For this reason, there is found a complete series of transi- 
tion shades, making w exact classification very difficult. 
Such a classification is also rendered somewhat unstable 
by the fact that environmental conditions, such as ex- 
posure to the sun's rays, have a marked effect upon skin 

Pigmentation, of <tk$ <eyes has proved ;a somewhat more 
fruitful index, insofar as it is unquestionably an hereditary 
tjrait. In the same connection may be mentioaed.JwV 
color. These traits, however, are also difficult to describe 
quantitatively because of continuous gradations. A 
further difficulty in the use of such criteria is their rela- 
tively narrow distribution, black hair and eyes being the 
universal rule outside of a single stock. 

In addition to coloring, other characteristics of the 
hair have been employed as differentiating signs. The 
texture of the hair is generally regarded as a valuable 
criterion of race classification. Fullness of the beard and 


degree of development of the downy hair which covers 
the body as a whole are also coming to be recognized as 
useful indices. 

Racial groups have been differentiated on the basis of 
gross bodily dimensions, chief among which is stature. 
Group differences in this respect are, however, surpris- 
ingly small and consequently of doubtful value in racial 
identification. Facial and cranial measurements have 
been employed to somewhat better advantage. Among 
the former, the most common are nasal index, which ex- 
presses the relative length and breadth of nose, and 
various indices of prognathism, or the degree of protru- 
sion of the jaws. Cranial capacity, or volume of the skull, 
yields rather ambiguous results because of its depend- 
ence on general body size and because of the wide variation 
within groups with consequent overlapping between groups. 
Cephalic index, 1 on the other hand, has proved to be 
one of the most satisfactory criteria of classification and 
is now widely employed. 

In view of the relative paucity of satisfactory anatomical 
criteria, attempts have been made to evolve physiological 
or biochemical schemas of classification. It has been 
suggested, for example, that races might be classified on 
the basis of the , blood groups which have become 
familiar in connection with blood transfusions (cf. 19). 
These blood groupings refer to the agglutinative reactions 
of the red blood corpuscles, i-.e., the tendency of such 
corpuscles to clump together- when the blood of certain 
individuals is mixed with that of certain other individuals. 
It is now well known that there exist so-called "universal 
donors" whose blood can be safely added to that of any 
individual, as well as "universal recipients" who can 

, , t. . ioo X head width 

1 Cephalic index = head 1 n th F r fuller descri P tion ? see Ch - 


safely receive the blood of any other person. There are, 
In addition, classes of persons who can receive blood from 
certain specific groups only, and who can likewise donate 
only to certain groups. Some data on the relative inci- 
dence of the various blood groups in different racial stocks 
suggest a possible relationship between the two, although 
tirejdiff^rentiation is by no means clear. A serious ob- 
jection to such a classification is that it cuts across and 
conflicts with the usual anthropological divisions obtained 
with other criteria. On the basis of blood groupings, very 
diverse groups would be lumped together indiscriminately. 

The endocrine glands have also played their part in race 
classification. Likenesses have been noted, for instance, 
between the physical and alleged mental characteristics 
of certain groups and those of pathological conditions 
associated with glandular dysfunction (cf. e.g., 22). Thus 
a parallel has been drawn between the cretin and the 
African pygmy. Pituitary enlargement has been attributed 
to the Hottentots and adrenal deficiency to the Negro. 
The "childlike" appearance of the Chinese has been 
ascribed to an over-active thymus. Such methods of 
classification are especially questionable for two reasons: 
they take a superficial and partial resemblance as their 
point of departure; and they reason from pathological 
conditions existing within a single group to the normal 
characteristics of entire groups. 

Finally, mention should be made of the efforts to deal 
with race^Jn^jter^^ (cf. Ch. IX). 

Kretschmer (25), for example, believes the ratio of lgto- 
sojnes and pyknic to differ in various racial groups and 
offers this as a possible explanation of the psychological- 
differences between such groups. Others, both prior and 
subsequent to Kretschmer, have attempted similar classi- 
fications. The reader should recall in this connection the 


difficulty of finding "pure types" and the absence of valid 
evidence for a correlation between the physical charac- 
teristics of such types and any of their alleged mental 


In addition to the special deficiencies of individual 
methods of classification discussed in the preceding section, 
certain major difficulties are encountered in the applica- 
tion of all, or nearly all, criteria of race. In the first place, 
a wide variability exists within any one group in respect 
to any trait. Closely related to this is the marked over- 
lapping between different groups in any of the criteria 
msgtioned. Thus, although two groups may differ sig- 
nificantly in average height, individuals can readily be 
found in the " shorter group" who are taller than certain 
individuals in the "taller group." This obviously makes 
group delineations indistinct and relatively arbitrary. 

A third difficulty is the inconsistency frequently found 
whetrmoi^tha^ one criterion is employed! An Individual 
might have the coloring of a Nordic, the cephalic index 
of an Alpine, and the stature of a Mediterranean. Or very 
dark skin pigmentation and woolly hair might be found 
in association with Caucasian features. Such instances 
are frequent and cannot be dismissed as exceptions. 

Finally, it should be noted that many of the, .ajjeged 

raaalj:.?iactenst}p8 yyiiich ^ere formerly heUsvacLto be 

stable and innate are bqing found ( .s^Qeptible tQ mviron- 
mmtal "influences. Even such apparently "hereditary" 
traits as body height, skull shape, and facial conformation 
have proved to be dependent in part upon stimulating 
conditions in early childhood. This was clearly demon- 
strated in the investigations of Boas (3) on the American- 
born children of immigrants from several European 


countries. These children were compared with foreign- 
born children from the same countries, who were also 
living in America. Differences were found in stature, 
weight, and length and width of head. 

The most striking indication of environmental influence, 
however, was furnished by an examination of the cephalic 
indices of two immigrant groups which differ markedly in 
head shape (3). American-born and foreign-born boys 
were compared within the east European Hebrew and the 
Sicilian groups living in New York City. The former 
are characteristically round-headed, having a high cephalic 
index; the latter are characteristically long-headed. As 
will be seen in Table XX, residence in the new envirpn- 
itiDeftfc- tends' to make the Jewish group more long-headed 
and the" Sicilian" more round-headed, both groups con- 
verging toward the American norna. It will also be noted 

~- < ,,S^.^w-S-v,,. ... - -"*' " 

that those boys born after a relatively long period of 
American residence of the mother exhibit a greater change 
than those born after a shorter residence period. This 
was also found to be the case in the data on other immi- 
grant groups. 

That these physical changes were the result of changing 
environmental conditions rather than selective factors 
was clearly demonstrated. A comparison of foreign-born 
persons who had immigrated at different periods showed 
no significant differences in the traits under consideration. 
The measurement of American-born and foreign-born 
children of the same parents^ furthermore, revealed differ- 
ences in the expected direction. 

The results of Boas have subsequently been corrob- 
orated by Guthe (17), who compared the cephalic indices 
of 187 Russian-born Jewish children and 127 American- 
born Jewish children in Boston. The cephalic indices 
found by Hirsch (18) on American-born children of 




(After Boas, 3, p. 10) 




Cephalic Index 

Foreign-born Sicilian boys 




American-born Sicilian boys : 

Born less than 10 years after 

arrival of mother 




Born 10 or more years after 

arrival of mother 




Foreign-born Hebrew boys 




American-born Hebrew boys: 

Born less than 10 years after 

arrival of mother 




Born 10 or more years after 

arrival of mother 




South Italian, Russian-Jewish, and Swedish parentage 
were also in general agreement with the corresponding 
figures reported by Boas. 

More recently, similar investigations have been con- 
ducted on Oriental groups. Spier (33) obtained a series, of 
anthropological measures on 320 American-born Japanese 
schoolchildren in Seattle, Washington, and its vicinity. 
The same measurements were repeated on 521 school- 
children living in those sections, of Japan from which 
most of the Seattle group was believed to have come. ,Jn 
general, the American-born children were larger, taller, 
more round-headed, and had .wider faces, than those born 
in Japan. Many of the individual comparisons of corre- 
sponding age and sex groups yielded statistically reliable 
differences between the American-born and native sub- 
jects. As IE. th^ case of the European immigrants, the 
differences tended to become more marked the longer the 
mother had lived in this country. 


A variety of factors have been proposed to account for 
the changes in physical type found in immigrant groups. 
Differences in bedding and cradling, as well as the gradual 
abandonment of swathing customs practiced in the mother 
country, have been cited as possible explanations of the 
changes in head shape. Nutrition and type of diet are 
doubtlessly important factors in all of the physical changes 
noted. Alteration in the activities of the endocrine glands 
under the stress of adjusting to a new culture has also 
been suggested as a possible factor (cf. 18). Most of these 
explanations are, to be sure, highly speculative. What- 
ever the specific influence or influences at work, however, 
it is quite definitely established that they are of an en- 
vironmental nature. 


It is apparent that no one criterion of race can yield a 
satisfactory classification. Nor can clear-cut group dis- 
tinctions be made with a combination of such criteria. 
It should be borne in mind that at best any racial classifi- 
cation is approximate. No sharp line of demarcation can 
be established between groups, nor can every individual 
be unequivocally assigned to one particular group. , TTft e 
classification which is most widely accepted., at .present is 
oneTTRi'^ of criteria, chief -among 

whicE^are'ceplialic index, hair quality, hiairiaess an the 
bodyTf acial conformation, aijid bpcJUy p^ppgrtians. An 
outline of this classification (cf. 26, p. 41) is shown 
below : 

L Caucasian or "white" 

1. Nordic 

2. Alpine 

3. Mediterranean 

4. Hindu 


II, Mongoloid or "yellow" 

1. Mongolian 

2. Malaysian 

3. American Indian 

III. Negroid or "black" 

1. Negro 

2. Melanesian 

3. Dwarf Black 

IV. Of doubtful classification 

1. Australian 

2. Polynesian 

3. Ainu 

4. Small, scattered Indo-Australian groups 

Within the Caucasian or white race, four subdivisions 
are generally recognized. Three of these groups are the 
Nordic, Alpine, and Mediterranean classes into which 
the population of Europe is divided; the fourth consists 
of the Hindus. The Nordics are described as tall, blond, 
blue-eyed, fair-skinned, and dolichocephalic, or long- 
headed. They occupy a horizontal belt around the Baltic 
and North Seas, covering most of England, northern 
France, the Scandinavian peninsula, Holland, and north- 
ern Germany. The Alpines, located chiefly in central 
Europe, are of medium stature and intermediate coloring, 
but definitely brachycephalic, or broad-headed. In the 
Mediterranean group, we again find a pronounced dolicho- 
cephaly, accompanied by black or brown hair and eyes, 
relatively dark skin, and short stature. As its name im- 
plies, this group is found on the shores of the Mediterra- 
nean, comprising most of the population of Spain and 
Portugal, southern France, southern Italy, Greece, and 
certain parts of northern Africa. The Hindu, although 
darker skinned, bears a very close resemblance to the 


Mediterranean and is sometimes included within this 

The Mongoloid race is characterized by straight hair, 
very little hair on the face and body, thin lips, and fre- 
quently the epicanthic fold which produces the appearance 
of "oblique" eyes. Short limbs are usually the rule in this 
group. Skin color may be yellow, brown, or reddish. This 
race comprises the Oriental Mongolian, as well as the 
American Indian and the Malaysian. All three are be- 
lieved to have evolved by differentiation of the same 
primary stock. Close and extensive observation shows the 
physical differences between these groups to be much less 
significant than is popularly supposed. 

The Negroid race has relatively long arms and legs, 
woolly hair, relatively little hair on the face and body, 
full lips, and a flat nose. In coloring, it is black or dark 
brown. This stock has been subdivided into the African 
Negro proper, the Oceanic Melanesian, and the Dwarf 
Blacks or "pygmies" found in equatorial Africa and other 
scattered locations. The Bushmen and Hottentots are 
also occasionally included under the Dwarf Blacks. 

There still remain certain groups of people of doubtful 
classification. These cannot be assigned definitely to any% 
one of the three major human stocks. These peoples 
exhibit the characteristics of more than one group and 
would thus be classified inconsistently with different sets 
of racial criteria. They include such groups as the Aus- 
tralian and Indo-Australian, the Polynesian, and the 
Ainu, a people of very low cultural status inhabiting an 
island off the coast of Japan. The Ainu have both Cau- 
casian and Mongoloid traits, but are characterized by a 
thick hair-covering on the entire body. The impossibility 
of classifying these groups is not a serious deficiency of the 
present schema, however, since they comprise only a very 


small segment of the human species. It has been esti- 
mated that about 99% of all mankind can be assigned 
to one or another of the three major races. 


Racial affiliation should not be confused with national- 
ity. A race is a biological group; it implies a certain 
community of hereditary background and is identified by 
physical criteria. A nation 3 on the other hand, is a, cul- 
tural, political, and geographic grouping. It has been a 
common practice, especially in the popular literature on 
the subject, to regard all the individuals of a given nation 
as members of a single race. This is far from the truth and 
can only yield very misleading results. Thus in France 
can be found representatives of all three European racial 
groups, depending upon the particular section of the 
country surveyed: in the extreme north the population is 
predominantly Nordic, in the large central portion Alpine, 
and in the southern part Mediterranean. Similarly, 
northern Germany is chiefly Nordic, but the southern 
portions are Alpine, In northern Italy the Alpine type 
predominates and in southern Italy the Mediterranean. 
It is apparent that racial classifications must be made on 
an individual and not a national basis. 

Another common source of confusion is that between 
racial and linguistic or philological categories. Thus the 
terms Latin, Aryan, Semitic, and Anglo-Saxon are fre- 
quently employed in popular discussion to signify races. 
But the groups which now speak languages of Latin origin, 
including French, Italian, Spanish, Portuguese, Rou- 
manian, and others, present an extremely varied racial 
composition and are not a unit in any but the philological 
sense. The term Aryan is likewise a very broad one applied 
by students of linguistics to all those peoples using a 


derivative of the original Indo-European language. Simi- 
larly, the terms Semitic and Anglo-Saxon refer to groups 
of languages and not to any biologically distinct groups of 
people. The loose use of national and linguistic nomencla- 
ture interchangeably" with racial designations has further 
~^coi^fic^ted-^n SilrQady difficult problem of classification. 
It is well to bear in mind the distinction between these 
various types of categories. 


An additional difficulty in the way of racial classifica- 
tion is introduced by the extensive amount of race mix- 
ture which has been going on for countless generations. 
Such mixture is particularly common among the sub- 
groups of the White race, so that as a result it is difficult to 
find Inany "pure" Nordics, Alpines, or Mediterraneans 
even in those regions which are supposed to be character- 
istically populated by these groups. Similar interbreeding 
has occurred to a greater or lesser extent among nearly all 
racial groups. There exist at present only a very small 
number of isolated primitive groups which may be re- 
garded as racially "pure." 

When the racial mixture has occurred in violation of 
social dictum or group mores, as in the case of Whites and 
Negroes in the United States, the problem of racial 
identification is further confused by the arbitrary classifi- 
cation imposed by society. Thus a "Negro" in many 
parts of the United States means an individual with any 
discoverable traces of Negro ancestry. Biologically such 
an individual may be much more closely affiliated with 
the Caucasian than with the Negroid race, but culturally 
he is a member of the Negro group and shares the social 
heritage of the latter. 

Race mixture, or miscegenation, is a problem which 


has aroused much discussion in its own right. Its ad- 
vantages and disadvantages have been argued at great 
length; enthusiastic exponents can be found for both sides 
of the question. Among those who consider miscegenation 
biologically injurious may be cited Davenport (9) who 
argues that race mixture produces physical as well as 
mental "disharmony/' the mixed group being a "badly 
put-together people," Negroes, for example, have rela- 
tively long limbs. Whites relatively short limbs. Inter- 
breeding between these two groups might, according to 
Davenport, result in individuals with long legs and short 
arms, or vice versa. Similarly, the mixture between a race 
with large teeth and large jaws and one with small teeth 
and small jaws might produce individuals with dispropor- 
tionate combinations of jaws and teeth. This is, in fact, 
offered by Davenport as a possible explanation for the 
frequency of tooth decay in the United States. 

The fallacy in this argument lies in its assumption that 
specific organs are inherited as unit characters. The rela- 
tion between an individual's bodily and mental traits 
and his gene constitution is, of course, much more com- 
plicated than that. In thcEIocess of growth, furthermore, 
all .parts of the organism interact and influence each 
othej^ development, thus producing a balanced and 
harmonious relationship of parts. 1 Observations on 
hybrids, both in the human and infrahuman species, 
reveal no significant disharmonies. The success of many 
animal breeding experiments certainly testifies to the 
beneficial results which may be obtained with race cross- 
ing. Physical measures of hybrid races have likewise 
shown either an increased physical vigor in the hybrid 
generation or a physical status which is midway between 
that of the parent groups. In no case has a consistent 

1 For a fuller discussion of these criticisms, cf. 5, 6. 


physical inferiority of a hybrid group been reliably estab- 

The effects of race mixture have also been discussed 
from the standpoint of the historical achievements of 
various groups (cf. 31). Two opposed theories have been 
proposed regarding the influence of race mixture upon the 
rise and fall of civilizations. On the one hand are cited 
ancient Egypt, classical Greece, and the Roman Empire, 
whose decline was coincident with the widespread inter- 
mixture with culturally inferior immigrant or servile 
groups. Similarly, the relative backwardness of certain 
present-day groups, such as are found in Mexico and 
South America, has been attributed to the fact that they 
are of hybrid stock. 

An equally strong case can be made, however, in sup- 
port of the opposite theory. Racial purity is often asso- 
ciated with a very low level of cultural development. 
Thus among the most racially pure human groups may 
be mentioned the hill folk of India, the Andaman Island- 
ers, and certain Eskimo groups. In our own country, the 
closest approximation to purity of racial stock is probably 
to be found among the southern mountaineers, a group 
notoriously backward in social and intellectual develop- 
ment. Conversely, the achievements of the modern 
world can be shown to be the cultural expression of 
hybrid stocks. All of the great European nations present 
a complexity of racial composition. The history of the 
United States furnishes a particularly striking example 
of the achievements of a highly mixed group. It can also 
be shown that many great men were the product of much 
interbreeding of diverse stocks. 

The apparent inconsistencies in such data arise from 
the attempt to establish a causal relationship between 
race mixture and cultural level. There is, in fact, no 


reason to expect a direct relation between the two. Both 
are in turn dependent upon a third factor, the degree of 
social contact or social isolation of a group. Cultural 
development is promoted by contacts between groups, 
with the resulting interchange of diverse material and 
intellectual products. At the same time, such contacts are 
conducive to race mixture. Hence a heightened cultural de- 
velopment is often found in association with race mixture.* 
In certain situations, social factors may cause the 
reverse relationship to hold between degree of racial 
purity and cultural development. Thus in a period of 
degeneration, miscegenation with a despised group may 
be tolerated as social barriers are lowered. In such a case, 
as in ancient empires in their decadent periods, the race 
mixture is but another symptom of a disruption of tradi- 
tional behavior and may temporarily coincide with a 
period of low intellectual achievement and cultural 
deterioration. In either case, the association is a superficial 
one, and cannot be employed to prove a biological basis of 
cultural development. 


It is apparent that the effects of race mixture cannot be 
determined by comparing the achievements of different 
groups or periods of history. Nor can an understanding 
of the problem be furthered by speculation on hypothetical 
biological influences. The .direct sxaroaatioa ot -hybrid 
individuals is more relevant fa v ths problem. A, few ,spat- 
te^ed groups of mixed racial .origin^ha^^been.tsgt^or 
% rveci , in Hawaii " (39), jamai<^'^^ 
elsewhere. The most extensive data, however, have been 

owing to the relative accessibjli^y^ol these groups in large 


Hunter and Sommermier (20) administered the Otis 
Group Intelligence Test to 711 American Indians attend- 
ingTihe Haskell Indian Institute at Lawrence, Kansas. 
The subjects ranged from fourteen years of age upwards. 
A widejvariety of tribes was represented. It was possible 
to, determine the degree of racial mixture directly by an 
examination of records of ancestry. No evidence was found 
of mixture with any race other than the White. The full- 
blood Indians formed the largest group, numbering 265. 
Only seven members of the entire sampling tested had 
less than i Indian blood. Individuals with such a small 
percentage of White blood would tend to become assimi- 
lated to the White population and attend the regular 
school rather than go to a special institute for Indian 
students. This may have introduced a selective factor in 
the data, since the mixed-bloods who attend Haskell are 
probably a poorer sampling of their group than the full- 
bloods. Such a selective factor, as the authors point out, 
would give an advantage to the full-bloods. 

ThLe.JiY.eiage.Qtis score of the Haskell group as a whole 
was, foundto be much lower than the White norms, age by 
age. s Withm the Indian group, a correlation of +41 was 
obtained between Otis score and degree of White blood, 
as determined from the ancestry records. Analysis of 
performance on the separate parts of the test showed the 
Indian groups to be most markedly inferior in the more 
highly verbal tests such as analogies, opposites, matching 
proverbs, and narrative jpmpletion. 

jJJ"'^^^ (Jartk ( r 6) analyzed the National 

Intelligence Test scores, o|15p^ 

bloojj, Indians attending^l^diaii, Reservation schools in 
Sout^, Dakota, Oklahoma, New -Mexico, and Colorado. 
A gKQUf) of 67 White children was, also tested for .compara- 
tive purposes. The intelligence test scores again showed a 


steady rise with decrease of Indian blood, the averages for 
f-bloods, f-bloods, and ^bloods being 74, 75, and 77.5, 
respectively. The correlation between degree of White 
blood and test score proved to be +4 2 - The data were 
further analyzed in respect to separate school grades. In 
Table XXI will be found the number of cases in each 
grade as well as the correlation between National Intelli- 
gence Test score and degree of White blood within that 
grade. It should be noted that the distribution of White 
blood was similar in all grades and could not therefore 
account for the differences obtained. 




(After Garth et al, 16, p. 274) 


Number of Cases 









1 80 








These data suggest rather strongly an environmental 
interpretation, of the correlation between degree of White 
Hood and intelligence test, performance. In t the lower 
grades,, those children with , a larger * percentage of Yhite 
hlppd,, clearly excelled their, fellows. In the three upper 
grades,, however, "the relationship is very low and barely 
significant. Thus continued education in a .common 
achopl seems to reduce and ev$n wipe out, the, Apparent 
eff ets of degree of Indian blood, 

Klineberg (23) reports an absence of linear relation 
between degree of Indian blood and test performance in a 
group of 100 Yakima Indians in the state of Washington. 


The tests were taken from the Pintner-Paterson Perform- 
ance Scale and were largely dependent upon speed. The 
Indians as a whole obtained lower scores than a group of 
100 White boys who had been similarly tested. Compari- 
son of full-blood and mixed-blood groups, however, gave 
conflicting results, the poorest scores having been ob- 
tained by those subjects with the most and those with the 
least Indian blood. 

The same general results have been obtained with the 
American Negro. In an early study, Ferguson (u) ad- 
ministered four simple psychological tests l to 907 Negro 
schoolchildren in three cities in Virginia. A^s^usjiajly the 
case 2 ' the Negroes as a group were most deficient in the 
iwqlverbal tests; in. the remaining two tests, the differ- 
ences were slight and inconsistent. The subjects were 
divided into four groups on the basis of skin color, hair 
color, and shape of the head and face. This classification 
was made by inspection only, no anthropometric measure- 
ments having been made. Oa, this basis, Ferguson esti- 
mated that there is a steady rise in general intellectual 
performance with increase of White blood. In view of^the 
crude method of classification employed, little weight can 
be'attached to such results. 

More recently, Peterson and Lanier (29) administered 
a numbeF of " rt ingenuity " tests as weir as intelligence 
scale? to 12-year-old Negro schoolchildren in Nashville, 
Cpcago, and New York City. Several of the tests s were 
non-language, an important consideration in the compari- 
son of facial groups with diverse'educatibi^ 
Ratings of skin color on a seven point scale were obtained 
on the Nashville and Chicago groups. In Table XXII are 
shown the correktions^^ J^ween^^htness ^ o^jk 
scores on the five tests employed. 

1 Analogies, sentence completion, A-cancellation test, and stylus maze. 






(After Peterson and Lanier, 29, p. 86) 


Number of Cases 


Binet group test 



Myers mental measure 



Rational learning, time score 



Mental maze, time score 



Disc transfer, time score 



In view of the inadequacy of skin color as a criterion 
of race, more extensive measures were obtained on the 
group of 75 New York City subjects. Correlations were 
computed between score on the Yerkes revision of the 
Binet Intelligence Scale and the four physical traits which 
were found to differentiate most clearly between White 
and Negro subjects. These correlations are shown in 
Table XXIII below. As will be seen, the correlations are 
all too low to indicate a reliable degree of relationship. 




(After Peterson and Lanier, 29, p. 90) 



Nose width 
Lip thickness 
Ear height 
Interpupillary span 

Composite of these four traits 





Klineberg (23), in the previously described investiga- 
tion with the Pintner-Paterson Scale, also tested 139 Ne- 
gro boys between the ages of 7 and 16 in rural sections of 


West Virginia. The correlation 1 between intelligence 
test score and three anthropometric measures indicative 
of degree of Negro blood are given below: 

Nose width .083 

Lip thickness .068 

Black pigmentation .12 

As in the study of Peterson and Lanier, the relationship 
between test performance and index of Negro blood is 
negligible when accurate measures are employed. 

The fact that a few investigators have found a positive 
relatlbifship between degree of White blood and intelli- 
geiice^test performance is considered very significant by 
those" who attribute a biological basis to race differences 
in intelligence. Thus it is argued that just such a rela- 
tio v nship would result from the mixture of a superior and 
an inferior stock, the mixed group being intermediate 
between the better and the poorer parent races. Similarly, 
the greater the contribution of the superior race to the 
individual's hereditary background, the higher should be 
his intellectual status. 

Such an interpretation fails to take into account those 
casesTn which negative results have been obtained under 
carefully controlled conditions. There are, furthermore, 
other possible explanations of the intermediate position 
of certain hybrid groups. In the first place, race mixture 
is often selective. This is especially true of those mixtures 
which are discouraged or frowned upon by society. In 
such cases, miscegenation may be confined largely to the 
socially and educatrorLally ^ mterior mqnabQrs of both groups. 
More often, perhaps, the selection occurs only in the 
group which is held to be "superior," there being no 
prejudice against such a mixture among members of the 

1 The influence of age was ruled out by the partial correlation technique. 


supposedly "Inferior" race. This was doubtlessly the 
case when an "advanced" and a "primitive" group first 
came into contact. It has also been suggested (ci. 31) 
that a certain amount of selection may occur in the reverse 
direction, the superior individuals of the "lower" race 
being chosen more often for such unions. It is doubtful, 
however, whether such a selection is made on an intel- 
lectual basis. It is apparent that the problem of selection 
in race mixture is a very complicated one which can 
only be settled by an analysis of actual historical and 
social developments in individual groups. The relative 
status of the hybrid and parent groups, therefore, will 
vary with the specific circumstances. 

In any discussion of race mixture, the social and cultural 
conditions imposed upon the hybrid group cannot be 
ignored. On the one hand, such groups are frequently 
stigmatized and may be despised by both parent groups. 
The hybrid individual is often made to feel that he belongs 
to neither group and that he stands apart from his fellow- 
beings. Such a situation may produce serious personality 
disorders, maladjustments, and anti-social behavior. As 
Reuter expresses it: "The hybrids tend to be distinct in 
social position, culture status, and personality organiza- 
tion: sociologically, as well as racially, they are hybrid" 
(3 1, p. vi). On the other hand, the hybrid individual often 
assimilates more readily than the full-blood to the cul- 
ture of the "superior" race. Because of the prevailing 
beliefs on the relative status of the two races, he is usu- 
ally considered to be more capable than his full-blooded 
cousins. As a result, he is given better educational oppor- 
tunities, admitted to more responsible positions, and 
afforded better facilities for advancement in every way. 

It flQted that the mixed-bloods have been 
exposed more directly tp tlu i 


customs of the "superior" group than have the full-bloods. 
Whether the miscegenation occurs through legal marriages 
or illicit unions, the presence of the White parent will on 
the whole tend to bring about a closer contact with the 
White culture than is the case in families where no such 
mixture has occurred. As a result, the economic and 
social level of the home, as well as the degree to which 
English is spoken at home, frequently differentiate hybrid 
from full-blood groups. This is particularly true of the 
American Indian. And it will be recalled that in this 
group a significant positive correlation between degree of 
White blood and intelligence test performance was found 
more often than in the Negro group. 


Many alleged " racial" comparisons have been made 
on immigrant groups in the United States. The subjects 
are usually classified according ,to country of birth; if 
American-born children of immigrants are employed, they 
are classified on the basis of parents' birthplace. Sjjch 
investigation^ camiat yield any information on the prob- 
lem of race differences. As has already been pointed out, 
national groups cannot be assigned as a whole tp one, or 
another racial .stock. But even Jpr the study of national 
differences such data, are inac^quate &nd, misleading. Im- 
migrants cannot be assumed, -to be representative ^sam- 
plings of their home population. They are not , drawn 
proportionately from all educational, ecQapmip^ ..awLspcial 
levels but usually represent a select gipup. 

A more serious difficulty is that such selective factors 
may operate differently in each country. A ffw a result, 
immigrant groups from different, ( paXions . 
samplings of their home populations nor 
themselves. If it coulcl be shown, for instance, that immi- 


grants from all nations were drawn consistently from the 
lower levels of society, then such groups would at least 
be comparable with each other. But it is well known 
that, through purely historical reasons, the immigrants 
from some nations may represent a relatively inferior 
sampling of their population, from others a more nearly 
random or average sampling, and from still others a 
relatively superior sampling. 

It has been frequently suggested, for example, that the 
superior performance of Chinese and Japanese children 
in America on our intelligence tests may be the result of 
selective factors, only the more progressive families emi- 
grating from these countries (cf., e.g., 8, 32). Many of 
the immigrants from southern Europe, on the other hand, 
are probably an inferior sampling of their own national 
population. In a recent study (13), Danish and Italian 
girls both in the United States and in Europe were ex- 
amined with the International Group Mental Test. Al- 
though the Danish samplings in this country excelled 
the Italian, no reliable difference was found between 
the groups tested in Copenhagen and in Rome. 

It is apparent that the testing of immigrants can throw 
little or no light upon the relative status of the national 
groups from which they are drawn. It might be argued, 
however, that the determination of the abilities and per- 
sonality traits of the immigrants themselves is of direct 
practical value for restriction of admittance, assimilation, 
and similar purposes. Such an argument fails to take 
into account two important aspects of the problem. In 
the first place, the behavior of immigrants may simply 
reflect their former environmental background. We can- 
not assume that the emotional and intellectual traits of 
such persons are innately determined just because they 
persist under the new environment. The influence of 


early conditioning is too strong to be readily wiped out. 
Similar traits would also be noticeable to a slighter extent 
in the offspring of immigrant parents, as long as family 
traditions and the practices of the home country en- 

A further point to note in the study of immigrant 
groups is that the immigration itself, with its resulting 
necessity of adjusting to a new culture, is an important 
environmental influence. This factor cannot be ignored 
in analyzing the mental and emotional make-up of the 
immigrant. The confusion of standards and shifting 
reference points contingent upon such an adjustment 
cannot fail to have an effect upon the subject's behavioral 
development. The point has frequently been made that 
the maladjustment is greatest not in the case of the im- 
migrating generation who retain their customs to a large 
extent, nor in the case of the third and succeeding genera- 
tions where adaptation and assimilation is virtually com- 
plete, but in the case of the offspring of the immigrants 
or second generation who are caught in the maelstrom 
occasioned by two different frames of reference. 

In an extensive survey with a revision of the Woodworth 
Personal Data Sheet, Mathews (2$) found a,, much. greater 
number of neurotic symptoms on the average among the 
cKilclren of immigrants thai} among those of native par- 
ffitage. The children tested ranged in age from 9 to 19 
and in school grade from the fourth to the twelfth. Both 
sexes were included in the study. The median number of 
neurotic symptoms* reported by each of the three major 
groups selected for comparison was as follows: 

"Mixed" group: largely of north European 
ancestry; resident in America for several 
generations (N = 87) 16 

Jewish group (N = 199) 20 

Italian group (N = 188) 36 


Data such as these do not constitute an adequate basis 
for the conclusion that Jewish or Italian groups in this 
country are by nature emotionally unbalanced. In a 
similar situation, the " normal" individual upon whom 
the test was standardized might have reacted similarly. 


1. Aristotle. The Politics of Aristotle, ed. by W. L, Newman. 
Oxford: Clarendon Press, 1887. Vol. I. Pp. 580. 

2. Blumenbach, J. F. Anthropological Treatises (transl. by 
T. Bendyshe). London: Longman, Green, Roberts, 1865. 
Pp. 406. 

3. Boas, F. Abstract of the Report on Changes in Bodily Form of 
Descendants of Immigrants. Washington: Gov't, Printing 
Office, 1911. Pp. 58. 

4. - . Anthropology and Modern Life. N. Y.: Norton, 1928. 
Pp. 246. 

5. Castle, W. E. "Biological and Social Consequences of Race 
Crossing," Amer. J. Phys. Anthrop., 1926, 9, 145-156. 

6. - . "Race Mixture and Physical Disharmonies," Science, 
1930, 71, 603-606. 

7. Chamberlain, H. S. Die Grundlagen des neunzehnten Jahr- 
hunderts. Miinchen: Bruckman, 1901. Pp. 531. 

8. Darsie, M. L. "Mental Capacity of American-Born Japa- 
nese Children," Comp. PsychoL Mon., 1926, 15, No. 3. 
Pp. 89. 

9. Davenport, C. B., and Steggerda, M. Race Crossing in 
Jamaica. Washington: Carnegie Inst. of Wash., 1929. Pp. 

10. de Gobineau, A. J. Essai sur finegalite des races humaines. 
Paris : Firmin-Didot, 1853. Vol. I, pp. 492; Vol. II, pp. 512. 

11. Ferguson, G. 0. "The Psychology of the Negro," Arch. 
PsychoL, No. 36, 1916. Pp. 138. 

12. Fischer, Eugen. Die Rehobother Bastar ds und das Bastar dier- 
ungsproblem beim Menschen. Jena: G. Fischer, 1913. Pp. 


13. Franzblau, R. N. " Race Differences in Mental and Physical 
Traits Studied in Different Environments," Arch. PsychoL, 
No. 177,1935' PP- 44- 

14. Garth, T. R. "A Review of Racial Psychology," Psychol. 
Bull, 1925, 22, 343-364. 

*5- Race Psychology: a Study of Racial Mental Differences. 

N. Y. : McGraw-Hill, Whittlesey House, 1931. Pp. 260. 

16. Garth, T. R., Schuelke, N., and Abdl,W. "The Intelligence 
of Mixed-Blood Indians," / Appl. Psychol., 1927, 11, 268- 

17. Guthe, C. E. "Notes on the Cephalic Index of Russian 
Jews in Boston," Amer. J. Phys. Anthrop., 1918, I, 213- 

1 8. Hirsch, N. D. M. "Cephalic Index of American-Born 
Children of Three Foreign Groups," Amer. J. Phys. An- 
throp., 1927, 10, 79-90. 

19. Hirszfeld, L., and Hirszfeld, H. "Seralogic Differences be- 
tween the Blood of Different Races," Lancet, 1919, 197, 
No. 5016, 675-679. 

20. Hunter, W. S., and Sommermier, E. "The Relation of 
Degree of Indian Blood to Score on the Otis Intelligence 
Test," /. Comp. Psychol., 1922, 2, 257-277. 

21. Huxley, J. S., and Haddon, A. C. We Europeans: A Survey 
of "Racial" Problems. London: Jonathan Cape, 1935. 
Pp. 299. 

22. Keith, A. "On the Differentiation of Mankind into Racial 
Types," Lancet, 1919, 197, No. 5013, 553-556- 

23. Klineberg, 0. "An Experimental Study of Speed and 
Other Factors in ' Racial' Differences," Arch. PsychoL, 
No. 93, 1928. Pp. in. 

24. . Race Differences. N. Y.: Harper, 1935. Pp. 367. 

25. Kretschmer, E. The Psychology of Men of Genius (transl. 
by R. B. Cattell). N. Y.: Harcourt, Brace, 1931. Pp. 256. 

26. Kroeber, A. L. Anthropology. N. Y.: Harcourt, Brace, 1923. 

Pp- 523- 

27. Linnaeus, C. v. Sy sterna Natures. Stockholm: Kiesewetter, 
1740 (Second edition). Pp. 87. 


28. Mathews, E. "A Study of Emotional Instability in Chil- 
dren," /. Delinq.) 1923, 8, 1-40. 

29. Peterson, J., and Lanier, L. H. "Studies in the Compara- 
tive Abilities of Whites and Negroes," Ment. Meas. Man., 
No. 5, 1929. Pp. 156. 

30. Porteus, S. D., and Babcock, M. E. Temperament and 
Race. Boston: Badger, 1926. Pp. 364. 

31. Renter, E. B. Race Mixture: Studies in Intermarriage and 
Miscegenation. N. Y.: McGraw-Hill, Whittlesey House, 
1931. Pp. 224. 

32. Sandiford, P., and Kerr, R. "Intelligence of Chinese and 
Japanese Children/' /. Educ. PsychoL, 1926, 17, 361-367. 

33. Spier, L. "Growth of Japanese Children Born in America 
and in Japan," Wash. State Univ. Publ. in Anthrop.^ 1929, 
3, No. i, 1-30. 

34. Watson, G. B. A Survey of Public Opinion on Some Religious 
and Economic Issues. N. Y.: Teachers College, Columbia 
Univ., Bur. Pub., 1927 (test blank and manual). 



In the preceding chapter it was shown that the classifi- 
cation of individuals into distinct races, as well as the 
choice of groups suitable for comparison, presents many 
difficulties. Even when a satisfactory selection of subjects 
has been made, however, additional problems remain to 
be solved. It is not sufficient to determine whom to 
measure. The questions what to measure and how to 
measure it are equally important. Thus it is necessary 
to decide which are the most significant traits for com- 
parison and what materials and techniques are applicable 
to the testing of culturally dissimilar groups. The in- 
terpretation of the obtained differences also raises im- 
portant questions. Is it possible to establish a universal 
criterion of "intellect" so that we may speak of one group 
as being intellectually "superior" and another "inferior"? 
What shall we use as norms or standards for the evalua- 
tion of widely diverse peoples? The latter is a very 
fundamental issue in differential psychology. 

Individuals who differ in racial affiliation also differ in 
many other respects. It is therefore very difficult to isolate 
the factor of race so as to determine its direct influence 
upon the subject's behavioral development. Members of 
different racial groups frequently speak different lan- 

1 For the sake of brevity, the term "race" will be employed without quota- 
tion marks or other qualifications to refer to groups so designated in the par- 
ticular investigation under consideration. It is not to be assumed, therefore, 
that such groups constitute races in the sense in which this term was defined in 
the preceding chapter. In each case, the nature of the groups will be apparent 
from the context. 



guages, a fact which greatly restricts the range of traits in 
which inter-group comparisons can validly be made. The 
differences in general educational opportunities and spe- 
cific type of training available to each group have an 
undoubted influence upon mental test performance. Such 
groups may likewise differ in their general social and 
economic level and in the facilities for intellectual advance- 
ment offered in their own homes. The background of 
tradition and culture against which the individual develops 
is also fundamentally diverse from group to group. The 
emotional attitudes, interests, ideals, and preferences fos- 
tered by such surroundings will not be the same. To this 
may be added the many difficulties arising when an ex- 
aminer from one racial or national group administers 
psychological tests -to subjects in another group. This 
situation is not comparable to the testing of subjects 
within one's own group. 

A considerable body of evidence is available which 
demonstrates the influence of the above factors upon 
mental test performance. Frequently such data were 
gathered incidentally in studies whose major purpose was 
the establishment of race differences in ability. A few 
investigations, on the other hand, have been conducted 
with the explicit aim of analyzing the pitfalls in racial 
comparisons. In either case, the data seem clear in their 
implication that factors other than race are operative 
in alleged racial differences. It should be noted that 
the question of race versus culture in the production of 
group differences is one phase of the general problem 
of heredity and environment. Race, it will be recalled, is 
a biological unit based upon hereditary community. Cul- 
ture, on the other hand, refers to the environmental con- 
ditions and behavior shared by the members of a single 



It is obvious that in the comparison of groups speaking 
different languages, verbal tests cannot be employed. 
Non-language and performance tests have been devised 
for this purpose. It is not to be concluded, however, that 
the same traits are being measured by all of these tests. 
As was shown in Chapter XI, many tests included under 
the heading of " intelligence scales " call into play widely 
different abilities. Thus when unfamiliarity with the 
language makes the application of verbal tests impossible 
in a given group, the range of processes which can be 
measured in that group is thereby narrowed. Tlysre is no 
substitute for verbal tests. It is a psychological impdssi- 
< EJn^*f5" 1 'fethhttiate i 'the'V'efbal content of a test without 
altering the mental processes involved. 

The effect of language handicap upon test performance 
isjBiost ; serious, however, when it is present in a mild 
decree. If the individual has a moderate understanding 
of English, it is usually deemed unnecessary to give him a 
non-verbal test. But such an individual may lack the 
facility in the use of English or the range of vocabulary 
required to compete fairly on a verbal test. This situation 
is often encountered in immigrants who have lived in 
America for many years, or in the children of immigrants. 
The latter are frequently bilingual, speaking their own 
language at home and English at school. .... 

That such relatively mild language handicaps may Kave 
ajgronounced effect upon intelligence test scores has-been 
frQSLuently demonstrated. Pintner and Keller (24) con- 
duqted a special investigation of this problem with chil- 
dren , pTlmlnigrants from several European countries. All 
of '.the children tested were in the kindergarten or the 
first two grades of elementary school. In order to deter- 


mine the effect of bilingualism upon test performance, 
the subjects were divided into two groups. The first 
group comprised all those from homes in which English 
was presumably spoken; in this group were included all 
children of American parentage, both White and Negro, 
as well as those of English, Canadian, Scotch, Irish, and 
Welsh parentage. In the second group were placed those 
who probably spoke a language other than English at 
home; these included chiefly children of Italian or Slavish 
immigrants, as well as a few whose parents had come 
from Germany, Greece, Hungary, Poland, and other Euro- 
pean countries. Both groups were given a revision of the 
Binet test. The average I.Q.'s obtained by each group, 
as well as the number of cases, are shown below: 

Number of Cases Average I.Q. 

English-speaking homes 367 92 

Foreign-speaking homes 674 84 

In one of the schools, these investigators were able also 
to administer the Pintner Non-Language tests to the 
second grade children. A comparison of the subjects 
from English-speaking and foreign-speaking homes on the 
twQ tests showed the latter group to be less inferior on the 
Non-Language test. The relevant data are given below: 

Number Average Average 

of Cases Binet LQ. Pintner LQ. 

English-speaking homes 49 99 109 

Foreign-speaking homes 56 89 103 

As a final check on the influence of language handica/p, 
the same authors compared the Stanford-Binet and per- 
formance test 1 scores of children referred to a psycholog- 
ical clinic for examination. The subjects were again 

1 Each child was given three or more of the following tests: Pintner Cube Test, 
Form Board, Witmer Cylinder Test, Healy Construction Puzzle A, and Mare 
and Foal Test. 


classified into those from English-speaking and those from 
foreign-speaking homes. This analysis corroborated the 
findings on the other groups. Among the foreign-speaking 
children, 75% obtained higher mental ages on the per- 
formance tests than on the Stanford-IB inet. In the 
English-speaking group, on the other hand, only 52% 
scored higher on the performance tests, i.e., there was no 
tendency for the group as a whole to excel in either test. 
Similarly, the average difference between performance 
scale and Stanford-Binet mental age was 16 months in 
the foreign-speaking group, as compared to an average 
difference of only 6 months in the English-speaking group. 
IJQ a later study, Pintner (23) analyzed the scores of 
third and fourth grade schoolchildren on the National 
Intelligence Test and the Pintner Non-Language Scale. 
The- subjects were classified into an " American" group, 
mostly of Irish descent, and a foreign group composed of 
children of Italian, German, or Polish parents. The 
percentages of "foreign" children who reached or exceeded 
the median of the 121 "American" children in each of the 
two tests are shown in Table XXIV. 




(After Pintner, 23) 

Nationality of Parents 

of Cases 

Pintner Non- 
Language Scale 

Intelligence Test 


I O2 




Total "foreign" 




It will be noted that in the total "foreign" group, as 
well as in each of the three national groups, the percentage 


reaching or exceeding the median of the American chil- 
dren is greater for the Non-Language than for the National 
Intelligence Test. On the Non-Language test, the " for- 
eign " group as a whole equals the performance of the 
American group, although it falls definitely below the 
latter on the National Intelligence Test. 

In an analysis of data secured independently by dif- 
ferent investigators, Goodenough (12) found a correla- 
tion of .75 between the average LQ. of children in 
various immigrant groups and the tendency of such groups 
to retain their own language for use in the home. An 
index of the latter was obtained by finding the ratio of 
the number of parents in each national group who had 
been in this country for a period of 20 years or over and 
had not adopted English, to the total number of parents 
in that group who had adopted it. The high negative 
correlation between these two factors indicates a strong 
tendency for children in those immigrant groups in which 
English is not readily adopted to obtain lower scores, on 
our intelligence tests. Goodenough points out that there 
are two possible explanations of such^a, finding. On the 
one hand, the lower intelligence test scores, of some groups 
may result directly from their greater language handicap. 
On the other hand, those national erpups in which English 

i , :t - f ,, v .- V ->.> W >,P W VW~"" - T'"" ' v? ' . 4,.'n.,, , .T^W^W ..' "?fGh'.*if 

is not commonly adopted ^ 

progressive from th^ outset. Thei^ialluje to learn Jfnglish 

would thus be the result of lower intelligence and poorer 

.,"">-. > r ;w, ,.,, ,,,. 1 ,^,., - ' " J"*.*." '"'""' ^' "''" ^~ '*'>'' |r ''^^* 


Neither interpretation can be selected solely on the 
basis of the correlation between the two factors. QJ&&T 

d&^jJ^m^^^^m,g^^t, -that, tja,e , f ormer jig. , tjxe .more 4? rob- 
able hypothesis. Thus, the inferiority of the immigrant 

" ""* . """" T ,. 'A'^-^'fe'i ..''*'".-' ' " jj v ' *'"' "'*""'. " " "' ' "" '" " VH 

groups is greatly diminished arid may.di^^ppear .^jj^rely 
when noa-language tests are f ^mplpyed.^ In tests such as 


the Stanford-Binet, on the other hand, it is well known 
that verbal facility plays 'a major part. The vocabulary 
test in the Stanford-Binet, for example, has been found 
to correlate so highly with performance on the entire 
scale that it has been proposed as a short substitute for 
the latter. In one investigation (14), this vocabulary test 
was administered to 562 public school children in a small 
industrial community in Pennsylvania, 90% of whom 
were of foreign parentage. The percentage of "foreign" 
children who scored at or above their age norms on the 
vocabulary test proved to be only 10, as contrasted to 
53.5 for the "American" group. It is apparent that such 
a group would suffer a severe handicap when tested 
with the Stanford-Binet or similar scales. 

The fact that immigrants from English-speaking coun- 
tries obtain relatively high average scores on intelligence 
tests, while those whose language is most unlike our own 
make a relatively poor showing, seems also to support 
the explanation in terms of language handicap. Further 
corroboration of this hypothesis is furnished by a study 
with the Otis Group Test on Italian children in New 
Jersey (20). When the subjects were divided into four 
language groups those who spoke only Italian at home, 
those who spoke Italian and some English, those who 
spoke English and some Italian, and those who spoke 
exclusively English a consistent rise in score was found 
with increase in amount of English spoken at home. 

The data on language handicap are not limited to 
immigrant groups from European nations. In investiga- 
tions on American Indians, the influence of language 
deficiency upon intelligence test performance has been 
vividly demonstrated. Jamieson and Sandiford (13) ad- 
ministered a series of standard tests to 717 pupils attend- 
ing Indian schools in Ontario, Canada. All of the children 


could speak English, but their ability to do so was below 
that of the average American child. The median LQ.'s 
obtained by the Indian children on each test are shown 

in Table XXV. 


(After Jamieson and Sandiford, 13) 


Number of Cases 

Median I.Q. 

National Intelligence Test 
Pintner Non-Language Test 
Pintner-Paterson Performance Tests 
Pintner-Cunningham Primary Test 




A comparison of the median I.Q. on the verbal and non- 
verbal tests reveals the influence of language handicap. 
On the National Intelligence Test, a predominantly verbal 
test, the Indian children are clearly below the American 
norms. On the Pintner Non-Language and Pintner- 
Paterson Performance Scales, on the other hand, their 
performance is practically up to the norms. The Pintner- 
Cunningham Test was administered to the younger chil- 
dren. In this test, the median I.Q. again proved to be 
low. It should be noted, however, that although this 
test does not involve the use of written English, rather 
detailed directions are given orally, a fact which would 
handicap the Indian child. 

A more conclusive demonstration of the importance of 
languarge^handicap was ftif iiislieci "By a comparison of the 
scores of a group of "monoglots," who spoke only English, 
wffiSjEose of "bilinguals," who spoke an Indian language 
at Jbome ^ror7Eart"ol the |ime. The median I.Q.'s of 
these two groups on each test are shown in Table XXVI. 
It will be noted that on the performance scale the bilingual 
children obtain a higher median LQ. ,JJW$^^ 




(After Jamieson and Sandiford, 13) 


Number of Cases 

Median I.Q. 





National Intelligence Test 
Pintner Non-Language Test 
Pintner-Paterson Performance 







Pintner-Cunningham Test 






whereas the reverse is true on the other three tests. This 

the bilinguals is not 

due to their inferior mental status but to the verbal na- 
ture of the test. In the case of the Pintner Non-Language 
Test, it is possible that the use of paper-and-pencil ma- 
terials gave a disadvantage to the children from the less 
highly assimilated homes. Those children who were rela- 
tively unfamiliar with such materials would also tend 
more often to come from Indian-speaking homes. 

Similar results have been obtained with Oriental groups 
in America. Darsie (7) tested 570 American-born Japa- 
nese children between the ages of 10 and 15. Only those 
children who reported that English was the language 
most familiar to them were included in this group. The 
linguistic difficulties were therefore not very pronounced, 
but were just such as might be commonly found among 
the children of immigrants. On the Army Beta, a non- 
language test, there was no consistent difference in score 
between Japanese and American children. The direction 
of the difference varied from one subtest to another; the 
total scores showed no significant difference at ages 10 
and ii and Japanese ' superiority beyond this. 


The Stanford-Binet, however, yielded clear-cut differ- 
ences. The median I.Q. of the Japanese group was 89.5 
as contrasted to 99.5 for White children of the same dis- 
tricts. That this difference was attributable to the verbal 
nature of the test was definitely demonstrated by a 
special analysis conducted by Darsie. Each individual 
test on the Stanford-Binet scale was ranked for degree 
of Japanese inferiority. The tests were then rated inde- 
pendently by seven psychologists on the basis of the 
degree to which success on each depends upon verbal 
ability. A final ranking of the tests was obtained by tak- 
ing the average of the ratings by the seven judges. When 
these two sets of ranks the one for Japanese inferiority 
and the other for "verbality" were compared, they were 
found to correlate +.87, Further corroboration of this 
relationship was furnished by a comparison of the per- 
formance of Japanese and Whites on the separate tests. 
Thus the superiority of the American children was found 
to consist chiefly in their greater success on the linguistic 
tests. The Japanese surpassed the Whites, on the other 
hand, in certain non-verbal tests of the Stanford-Binet 
scale involving sustained attention and visual perception. 1 


n,t^ other special diffi- 

culties are encountered in ^ u the , attenapt to administer 
tests "to widely differing groups. The use of pantomime 

^**ii*-wwfc l fc*lt,t..A,'J)'W,'w ','*' "' * ' ' " " : " ' ' ' J "" 1 "* 

and gesture in non-language tests is often confusing to 
the subject since it is not his normal mode of communica- 
tion. This is illustrated in certain observations regarding 
the administration of the Army Beta to the Negro draft 
in the United States army. Several examiners called 

1 The Japanese children were reliably superior in the Induction, Paper Cut- 
ting, Code Learning, and Enclosed Boxes tests. 


attention to the fact that it was difficult to keep up their 
subjects' interest in the test. In the report from one 
camp, it was stated that, "it took all the energy and 
enthusiasm the examiner could muster to maintain the 
necessary attention, as there was a decided disposition 
for the Negroes to lapse into inattention and almost into 
sleep' 5 (27, p. 705). One of the reasons offered in explana- 
tion of this reaction was the artificiality of the situation 
produced by the elimination of language. It is also 
difficult to standardize directions given in pantomime and 
to insure that they shall always be repeated in identical 

The use of pictures as test materials is also somewhat 
questionable, especially among certain groups who have 
had no experience with pictorial representation in their 
everyday life. A two-dimensional reproduction of an 
object is not a perfect replica of the original; it simply 
presents certain cues which, through the influence of past 
experience, lead to the perception of the object. If the 
cues are highly reduced, as in a simplified or schematic 
drawing, or if the necessary past experience is absent, 
the correct perception may not follow. It might be added 
that pictures of objects which are themselves unfamiliar 
in the cultural group to be examined are obviously un- 
suitable as test materials. They have, nevertheless, been 
included in certain non-language scales 1 which have been 
employed in racial comparisons. 

A further problem arises in connection with rapport. 
Test manuals repeatedly urge that the examiner must 

1 Such as the Army Beta and the Pintner Non-Language Scales. It might be 
mentioned that the International Group Mental Test is at present the most 
satisfactory scale for the comparison of widely varying cultural groups. In it a 
definite attempt has been made to include only items which are universally 
familiar, although possibly not to the same degree in every group (cf. Dodd, 8, 
Blackwood, 5). 


establish the proper rapport with his subjects. By this is 
meant, in general, that the testees should be put at their 
ease, their interest and cooperation should be secured, and 
they should be made calm and comfortable before the test 
is begun. In other words, it is assumed that each subject 
will be in a condition to do his best. In an individual 
test a definite effort is usually made to establish rapport 
with the subject. With group tests, however, this is 
much more difficult. The examiner in such a case must 
limit himself to a few reassuring introductory remarks 
and to the elimination of any obvious handicaps under 
which individual members of the group may be laboring. 
For this reason, group tests are frequently considered 
less accurate than individual tests. 

When an examiner, from. ,one cultural or racial group 
administers a test to subjects in a different group, rapport 
is even poorer, the situation being much more strained 
and unnatural for the subjects than when they are tested 
by a member of their own group. This is particularly 
noticeable in the testing of American Indians and Negroes 
by a White examiner. In addition to the racial disparity, 
the presence of a stranger will in itself occasion more 
emotional disturbance among the members of certain 
cultures than it would among American city schoolchil- 
dren who are accustomed to sudden visits from a suc- 
cession of supervisors, research workers, psychologists, 
and others. Furthermore, the suspicion and hostility 
manifested by many "primitive" peoples towards strangers 
will necessarily affect the individual's attitude and re- 
sponsiveness towards a foreign examiner. 


It is well known that the educational facilities available 
to the individual vary widely from one racial or national 


group to another. This is apparent even if we consider 
only the total duration of school training. 1 The irregularity 
of school attendance prevalent in certain groups, such as 
the American Indian, reduces still further the effective 
length of time devoted to instruction. Finally, the quality 
of the available training and the conditions under which 
it is obtained cannot be ignored. In general, it is just 
in those groups which receive the least schooling that the 
quality of instruction is poorest. The type of education 
offered in rural Negro schools of the South, for example, 
is far inferior to that in the average White public school. 

Contrary to a rather prevalent belief, intelligence tests 
are not independent of educational background. Thus in 
one investigation (15), several common intelligence tests 
were found to correlate as highly with standardized tests 
of school achievement as they did with each other. Sim- 
ilarly, an analysis of the army data showed a close cor- 
respondence between median Army Alpha score and aca- 
demic level attained. These data are summarized in 
Table XXVII. Within any one group, there is a consistent 
rise in median Alpha score with increase in amount of 
education. That differences still exist when comparisons 
are made vertically, within a single educational class, is 
attributable to a number of factors. Chief among these 
are differences in the quality of education, a factor which 
is ignored in the system of classification here employed. 
Differences in the social and economic level of the home 
as well as other more general conditions may also be 
mentioned in this connection. 

The reverse explanation has occasionally been proposed 
to account for the relationship between educational level 
and intelligence. Thus it is argued that the more intelli- 

1 In rural sections of the United States, for example, the school year is often 
drastically shortened, sometimes to as little as six months. 





(After Yerkes, 27, Part III, Ch. 10) 


Elementary School 





0-4 Years 

5-8 Years 

White officers 






White native-born 







White foreign-born 







Northern Negroes 
Southern Negroes 





gent individual will be more successful in his school work 
and will pursue his education further than the less intelli- 
gent. Intellectual differences are regarded as the cause 
rather than the effect of educational differences. Persons 
in the higher educational groupings would thus represent 
a more highly selected sampling from the,, outset. This 
explanation seems unnecessary in view of the obvious 
lack of adequate educational facilities among the sup- 
posedly less intelligent groups. Wjien opportunities for 
continued education or for satisfactory instruction at any 
level are so unlike from one group to another^ failure to ob- 
tain such education cannot be attributed to inferior intelli- 

The effect of educational handicap upon intelligence 
test performance is especially apparent in the American 
Negro. Since his native language is English, the Negro is 
frequently tested with the common verbal type of intelli- 
gence test. Because of his pronounced educational defi- 
ciency, however, the Negro has a very limited command 
of the language, as well as serious gaps in other fields of 
knowledge. A comparison of the median Alpha and Beta 


scores obtained by the Negro and White draft in the 
United States army is of some interest in this connection 
(cf. 27, p. 764). These medians were as follows: 

Alpha Beta 

White 58.9 434 

Northern Negro 38.6 32.5 

Southern Negro 12.4 19.8 

Although the relative standing of the three groups re- 
mains the same on the two tests, the actual differences 
among them are greatly reduced on the Beta. This test 
is not only non-language, but it is much less dependent 
upon educational background in general than is the Alpha. 


As was demonstrated in Chapter III, the type of home 

,,, , , - , * , , , ^ .,, ..,,,, ,, ,,. < A ' A 

in which the individual is reared exerts a pronounced 
effect "'upon his intellectual development. It is apparent 
that the economic, social, and cultural level of the homes 
of such groups as immigrants, Negroes, or American 
Indians is far below the general American average. Arljtt 
(2) conducted a special investigation to determine thp 
j n ^j^"'^^^Q^p or " occupational status upon racial 
^^rences in intelligence ,t?.st performance. THe Stanford- 
Binet was administered to 191 American children of 
native-born White parents, 87 children of Italian immi- 
grants, and 71 Negro children. All of the subjects were 
taken from a single school district and all spoke English 
with no apparent difficulty. Each child was classified on 
Taussig's five-point scale on the basis of father's occupa- 
tion; this was taken as an approximate index of the social 
and economic level of the home. 

When the three racial groups were compared as a whole, 
the following median LQ.'s were obtained: 


Native White 206.5 

Italian 5.0 

Negro 834 

The differences in occupational level among these three 
groups were, however, very large. Over 90% of the Ital- 
ians and Negroes fell into the "inferior" or " very inferior" 
classes on the Taussig scale. When only the children in 
these two occupational levels are included, the median 
I.Q. of the native White group drops to 92.0. Thus the 
intellectual differences among the three racial groups are 
reduced to a very small quantity when comparisons are 
restricted to children of the same social or economic 

It might again be objected that we cannot determine 
which is cause and which is effect in the relationship be- 
tween intellectual and occupational level. Since, however, 
the opportunities for employment in higher positions are 
far from equal for native Americans and immigrants, and 
this difference is still greater when Negroes are considered, 
it seems unwarranted to attribute the lower occupational 
status of the latter groups to inferior intelligence. 

In investigations on American Indians, the relatively 
low socio-economic level of the home is an important 
factor to be considered in the evaluation of their test per- 
formance. Opportunities for intellectual development, as 
well as the general level of material comfort, are far below 
the average for American homes. Thus in the study by 
Jamieson and Sandiford (13), the homes of the Indian 
children received an average rating of only 13 points on 
the Chapman Socio-Economic Scale, as compared to the 
White norm of 56 points. A close correspondence between 
the social status of various Indian groups and their rela- 
tive standing on the National Intelligence Test was found 
by Garth (n). 



A further factor in the behavioral development of the 
individual is the particular locale in which he lives, the 
tempo of the life about him, and other conditions charac- 
teristic of his general surroundings. This,. .represents a 
broader environmental background than that furnished 
by his own home. The first striking demonstration of the 
wide variations in intelligence existing within the native 
White population from different parts of our own country 
was furnished by the army data (27, Part III, Ch. 5). 
When the distributions of Alpha and Beta scores were 
tabulated separately for each state, distinct regional dif- 
ferences appeared. 

In a subsequent analysis (i) of the army data, median 
Alpha scores were computed for each of 41 states. Seven 
states were omitted from these calculations because of 
insufficient data; only those states were included from 
which records of at least 500 men were available. The 
states obtaining the ten highest medians and those ob- 
taining the ten lowest are shown below. It might be 
added that, owing to changing economic and educational 
conditions, this rank-order probably does not hold at 

Median Alpha c tafe Median Alpha 

Score Score 

1. Oregon 79-9 3 2. New Jersey 48.7 

2. Washington 79.2 33. South Carolina 47.4 

3. California 78.1 34. Tennessee 47.2 

4. Connecticut 73-6 35- Alabama 46.3 

5. Idaho 73.5 36- Louisiana 45.2 

6. Utah 72.2 37. North Carolina 43.2 

7. Massachusetts 71.6 38. Georgia 42.2 

8. Colorado 69.7 39. Arkansas 41*6 

9. Montana 68.5 40. Kentucky 41.5 
10. Vermont 67.5 41. Mississippi 41.2 


Since only the distribution of the White draft was con- 
sidered, the percentage of Negro population in the various 
states does not enter into these results. Similarly, the 
differences cannot be attributed to an influx of foreign 
immigration into certain states, since a correlation of 
.61 was found between Alpha medians and percentage 
of native-born population in each state. It was therefore 
the states with a greater proportion of native Americans, 
rather than those with a large foreign population, which 
tended to have the lower Alpha medians. 

Several interesting correspondences were noted between 
the rank-order of the 41 states for intelligence and a num- 
ber of other factors. Thus high positive correlations wqre 
found between indices of the economic level of each state 
and their median Alpha scores. The educational facilities 
witKin each state also corresponded closely with the Alpha 
ranks. The states were ranked for the efficiency of their 
educational systems on the basis of such information as 
percentage of daily school attendance, percentage of chil- 
dren attending high school, average per capita expenditure 
for education, teachers' salaries, etc. 1 The educational 
ranking for the year 1900 was employed in this analysis, 
since 1900 was approximately the time when the average 
man in the draft had been of school age. The two sets of 
ranks, those for Alpha score and those for educational 
efficiency, correlated .72 with each other. 

The relative influence of race and environment upon 

r^^www^^ , , , m ,, f^ 

intelligence test performance is rather vividly illustrated 
by a comparison of the median Alpha scores of ' tEe "White 
draft from the less ."progressive** ""states" 'wKK'TEe Scores 
of the Negro draft from the more progreTsivie "^states 
(cf. 27). A few of these medians jre shown Below: 

1 The Ayres rank-order of educational efficiency for each state was employed 
for this purpose. 







New York 



These figures suggest the degree to which environmental 
stimula^ allegeH/jaaaT differences in in- 

tellectual capacity. They also indicate the extensive over- 
lapping in intelligence test performance which exists be- 
tween the Negro and White groups in the United States. 
A consistent difference has also been found between the 
intellectual level of northern 'and 'southern Negroes. This 
wasT again shown by the army data (27). The median 
Alpha scores of northern and southern Negroes were 38.6 
and 12.4, respectively. On the Beta, the median scores of 
these two groups were 32.5 and 19.8. Similar results have 
been obtained in studies on Negro schoolchildren in north- 
ern and southern states (cf., e.g., 6, 22). In^certain local- 
ities, the Negro child's performance shows no inferiority 
to that of ffie' White child; tin bthefs, the difference between 
the two groups is very striking. Two explanations have 
been"*6ffered to account for the intellectual differences 
between northern and southern Negroes. 

attributes the differences to sele ctive ^migration. Thus the 
more intelligent Negroes, who have more initiative and are 
more progressive and capable of adjusting to a new en- 
vironment, would be more likely to migrate to the North. 
The second hypothesis explains the superiority of the 
northern Negro in terms of,^^^^^^/,^^^ such as 
better educational facilities and other opportunities for 


associates Xlj) , -t^Y^^/P^^Wsid^r^ble light ^ppn the 
relative validity of these two hypotheses. The problem was 



approached in two ways. In the first place, the relative in- 
tellectual status of Negro children whose families migrated 
to the North was investigated by comparing their former 
grades in southern schools with the norms for those 
schools. In this part of the study, the records of 562 Negro 
children who had moved to the North from three southern 
cities l were examined. Since all grades were transmuted 
into a percentile scale, 50 points represents the average 
status and this figure may be employed as a standard of 
comparison. The average percentile rating of those 
children who had moved to the North proved to be 49.3, 
winch is not significantly different from the general aver- 
age^ It is thus apparent that, at least in these groups, 
there was no tendency for the initially more intelligent 
children to migrate. 

A second Approach to, the problem was the comparison 
of intelligence test scores obtained by groups of Negro 
schoolchildren who had lived in New York City for differ- 
ent periods of time. The subjects were examined with a 
variety of standard tests, including the Stanford-Binet, 
performance scales, and several common group tests. 
Over 3000 Negro children in the Harlem district of New 
York City were employed. The subjects in tk^ different 
^^dence^^roup^s were equated f pi:, .age and ,sex;, they all 
attended the same schools and were approximately equal 
in social and economic background, the only important 
difference between them being the number of y$$fs spent 
in New York City. A group of Negro schoolchildren born 
in New York City was also included for comparison. 

In Table XXVIII will be found the average scores of 
each residence group on the National Intelligence Test, 
the Stanford-Binet, the Pintner-Paterson Performance 
Scale, and a paper-and-pencil form board test. In both the 

1 Nashville, Term., Birmingham, Ala., and Charleston, S. C. 





(After Klineberg, 17) 

National Intelligence Test 


Length of 



Length of 




of Cases 



of Cases 


1-2 years 



Less than one 




3-4 years 


7 6 

i2 years 



5-6 years 



2-3 years 



7-8 years 



3-4 years 



Over 8 years 



Over 4 years 






New York-born 



Paper Form Board 


Length of 



Length of 




of Cases 



of Cases 


1-2. years 



Less than 2 




3-4 years 

25 - 


2-5 years 



5-6 years 



Over 5 years 



7-8 years 



9-10 years 



Over 10 years 



New York-born 






* This figure is misprinted as 88.5 in the Klineberg monograph (17, p. 46). 

National Intelligence Test and the Stanford-Binet, there 
is a progressive rise in average score with increasing 
length of residence in New York City. It is interesting^ 
note that the groups bornjn^th^^^ 
jy^ w foq were bqyiLin titcSouth 

but had' lived 'inj%wj^ PH*^ This fact, 

as well as tile consistent increase in score with < lengtE^of 
NewTork,' City residence^ ^^tencls to support the environ- 


mental rather than the selective factor hypothesis. Fur- 
ther corroboration of this explanation is furnished by the 
fact that the differences between successive residence 
groups are greater on the National Intelligence Test than 
on the Stanford-Binet, the former being also more closely 
dependent upon environmental stimulation and schooling. 
Finally, it will be noted that on the two performance tests, 
the paper form board and the Pintner-Paterson, the re- 
sults are less consistent than on the linguistic tests. Al- 
though the groups having the longer New York City 
residence tend in each case to be superior, the position of 
individual groups is ambiguous. This is to be expected 
from the fact that the existing environmental differences 
have less effect upon performance tests than upon tests of 
a more verbal nature. 

It might be argued that the Negroes migrating to the 
North at different times may not be directly comparable. 
Thus the quality of the migrants might be deteriorating 
and this would account for the lower averages obtained 
by the later groups. This question was investigated di- 
rectly by testing two groups of twelve-year-old boys on 
two successive years. At the time of testing, each group 
had spent an equal length of time in New York, although 
they had migrated in different years. No evidence was 
found for a decline in the quality of immigration within 
this two-year period, the later migrants being, in fact, 
superior in nearly every comparison. Anthropometric 
measurements of different residence groups were also 
taken. These showed no difference among the groups in 
the possession of negroid traits. Race mixture could not 
therefore have been a factor in producing the intellectual 
differences among such groups. 


jdsfed M lQ jpt^lligence, test jperformance had been 


previously suggested In several other studies on Negro 
schoolchildren (cf., e.g., 19, 21). The series of investiga- 
ti6Hs"3ifected by Klineberg established this fact more 
conclusively. These findings, together with the data on 
the school achievement of Negro children before migration 
to the North, furnish definite evidence that the regional 
differences in the intelligence of Negroes are to be under- 
stood in terms of environment and not selective migration. 


The particular culture in which the individual is reared 
may influence his behavioral development in many ways. 
The operation of environmental forces, is not limited to,, the 
3^ quality of educational opportunities available 

in the school, the home, and the neighborhood. The ques- 
fiofTisTnot only one of amount, but of kind. The experi- 
ences of people living in different cultures may vary in 
such a*w*ay as to 'fetid a different meaning to their actions, 
stimulate the development of totally different interests, 
and furnish diverse ideals and standards of behavior. 

The importance of motivation and interest in intelli- 
gence Te^'^i^ffialTce, has been repeatedly emphasized. 
YeFtt is apparent that many of the tests in current use 
cannot arouse the same emotional reaction, in.oxher cul- 
tures as they do in our own. Thus for an American school- 
child, the average intelligence test bears a close resem- 
blance to his everyday school work, which is probably the 
most serious business of his life at the time. He is therefore 
easily spurred on to exert his best efforts and try to excel 
his fellows. For an Indian child, on the other hand, the 
same test cannot have such a significance. This type of 
activity has no place in the traditional behavior of his 
family or tribe. Similarly, many investigators have noted 
that among Negro children interest in intelligence tests 


is not as keen as among White children, and that the for- 
mer seem not to be as strongly motivated as the latter. 

In addition to emotional and motivational factors, 
special customs and traditions peculiar to one group may 
influence the subject's behavior in a test situation. Several 
curious examples of such traditional behavior have been 
reported. Thus Porteus (25), in administering perform- 
ance tests to Australian aborigines, found it difficult to 
convince his subjects that they were to solve the problems 
individually and without assistance. In explanation of 
this behavior, he writes: 

. . . the aborigine is used to concerted thinking. Not only 
is every problem in tribal life debated and settled by the coun- 
cil of elders, but it is always discussed until a unanimous de- 
cision is reached. On many occasions the subject of a test was 
evidently extremely puzzled by the fact that I would render 
him no assistance, especially when, as happened in the centre, 
I was testing some men who were reputedly my tribal broth- 
ers. This was a matter which caused considerable delay as, 
again and again, the subject would pause for approval or 
assistance in the task (25, p. 308). 

Similarly, Klineberg (18) reports that among the 
Dakota Indians it is considered bad form to answer a 
question in the presence of someone else who does not 
know the answer. This creates a particularly difficult 
situation in school, where the teachers find it difficult to 
induce the children to recite in class. In the same group, 
custom forbids one to answer a question unless he is ab- 
solutely sure of the answer. The effect which this would 
have upon intelligence tests in which the subject is ad- 
vised to "guess" when not sure and is urged to "try his 
best" on a difficult problem, can readily be foreseen. The 
child who refuses to give any answer unless he is certain 
of its correctness will lose many points which he might 


have earned through partial credits and chance successes. 
Another medium through which the cultural background 
may influence mental test performance is the special 
associations and meanings which have been built up by 
social conditioning. In one of the subtests of the National 
Intelligence Test, the child is required to underline the 
two words which tell what the given item always has. 
One of the examples in this test reads : 

Crowd (closeness, danger, dust, excitement, number). 1 

Although " closeness" and "number" are given in the key 
as the correct answers, it was found that, among Plains 
Indians, "danger" and "dust," or even "excitement," 
were frequently underscored. The experience which these 
children had had with crowds on the prairie had taught 
them that these were necessary attributes of a crowd 

(cf- 9)- 

Many similar instances can easily be found (cf., e.g., 18). 
In one of the tests of the Army Alpha, Form 6, occurs the 
question, "Why should all parents be made to send their 
children to school?" Of the several alternative answers 
given, the "correct" one is that "school prepares the 
child for his later life." But this is not true for the Indian 
child, whose schooling often unfits him for life on the 
Reservation. In a sentence completion test of the National 

Intelligence Scale is found the statement," should 

prevail in churches and libraries." The word to be inserted 
in this case is "silence." Among Negro children, however, 
this problem would be complicated by the fact that their 
own churches are seldom silent. Noise is not only common 
in their houses of worship but is frequently an integral and 
essential part of the ritual. 

A further example of the inapplicability of a mental 

1 Scale A, Form i, Test 3, Exercise 17. 


test to groups differing from the one upon which it was 
constructed is furnished by an incident which occurred in 
the testing of children in the Kentucky mountains. 1 The 
following is one of the problems in the Binet Scale: "If 
you went to the store and bought 6 cents worth of candy 
and gave the clerk 10 cents, what change would you 
receive?" One alert young boy, upon being asked this 
question, replied, "I never had 10 cents, and if I had I 
wouldn't spend it for candy, and anyway candy is what 
your mother makes." Still wishing to find out if the child 
could subtract 6 from 10, the examiner reformulated the 
problem as follows: "If you had taken 10 cows to pasture 
for your father and 6 of them strayed away, how many 
would you have left to drive home?" The child now re- 
plied promptly, "We don't have 10 cows, but if we did and 
I lost 6, I wouldn't dare to go home." The examiner tried 
once more with the following inquiry: "If there were 10 
children in a school and 6 of them were out with the 
measles, how many would there be in school?" This 
answer came even more promptly: "None, because the 
rest would be afraid of catching it too." 

Finally, mention should be made of the important role 
of speed in nearly all intelligence tests and of the widely 
varying emphasis placed upon speed in different cultures. 
An investigation by Klineberg (16) on Indian, Negro, and 
White -schoolboys illustrates, the operation of this factor. 
Several t>f the tests in the Pintner-Paterson Performance 
Scale were administered to the following groups: 

107 Whites in Toppenish, Washington 2 
120 Indians at the Yakima Reservation, Washington 
136 Indians attending Haskell Institute in Kansas 
139 Negroes in a rural district of West Virginia , 

1 This incident is reported in Pressey, S. L., Psychology and the New Education. 
N. Y.: Harper, 1933. Pp. 237-238. 

2 In the heart of the Indian Reservation. 


25 Whites in the same district of West Virginia 
200 Negroes in New York City 
100 Whites in New York City 

In accuracy of performance, a,s, measured by the, number 
of errorsHDiT e ach test, the Indians excelled the Whites, 
. were either equal or slightly superior to 
ites. All measu^ hand, 

the Volutes. A comparison of groups of the same 
race bu^limng ta in t dif^ent environments suggested that 
these differences in speed were cultural rather than biologi- 
calT^Thu^ the New York City Negroes clearly excelled the 
West Virginia Negroes in every comparison. Similarly, 
the Haskell Institute Indians were consistently faste* 
than those tested on the Ya f kima Reservation. A further 
the Haskell group into those who had previously 

lived on a Reservation and those who had lived among 
Whites irT a town or city showed the latter to excel ii> 

In explanation of these results, Klineberg calls atten- 
tion to the relatively insignificant part which speed plays 
in the life of the Reservation Indian or the rural southern 
Negro. Most observers are impressed with the Indian's 
almost complete lack of concern with speed. Time means 
nothing in the daily activities of the Indian. He can see no 
reason for hurrying through a task, especially if he finds it 
congenial and interesting. Thus insofar as the examiner 
arouses the child's interest in the test, he makes the 
necessity of speeding appear even more absurd. At 
Haskell Institute, on the other hand, time is much more 
important than on the Reservation. The students are 
constantly kept busy with a variety of tasks and thtf 
entire day is carefully scheduled. The White teachers t 
too, foster the attitude that it is desirable to finish things 
as quickly as possible. Similarly, the New York City 


Negroes have been exposed to the hustle of life In a big 
metropolis, whereas the rural Negroes are adapted to a 
much slower tempo of activity. 


In all group comparisons, there is a tendency to go 
beyond the actually observed differences in behavior and 
to evaluate the relative status of each group in terms of 
some presumably universal criterion. Linear comparisons 
are made in terms of better or worse. Thus we frequently 
find national or racial groups arranged in a rank-order for 
"intelligence." One group is said to be "superior," 
another "inferior" in its mentality. Such a point of view 
implies either that one group is consistently poorer than 
another in all mental traits, or that certain behavioral 
processes are universally more significant, more valuable, 
or even more "mental" than others. 

In regard to the first of these assumptions, it can easily 
be shown that racial or national groups vary in the relative 
inferiority or superiority which they manifest in different 
traits. Thus Japanese children have been found to excel 
White children significantly in tests involving sustained 
attention, visual perception, or spatial orientation, while 
falling behind on verbal or arithmetic tests. This was 
demonstrated in Darsie's study (7) by the relatively 
superior performance of the Japanese children on four of 
the Stanford-Binet tests, viz., Induction, Paper Cutting, 
Enclosed Boxes, and Code Learning, as well as on the 
Digit-Symbol Learning and the Number Comparisons tests 
of the Army Beta. A slight superiority was also shown by 
these children in the Cube Analysis and Geometric Con- 
struction tests of the Beta Scale. 

Similarly, differences in specific traits have been found 
when comparing European immigrants in this country 


(cf. 5 e.g., 4). Italian children in general do relatively well 
on performance tests and relatively poorly when examined 
with abstract or linguistic materials. Jewish children, 
on the other hand, excel on verbal tests and fall behind in 
problems dealing with concrete objects and spatial rela- 
tions. This difference may be accounted for on the basis 
of the cultural traditions of the two groups. Among 
Jewish families there is a marked emphasis upon the 
formal aspects of education and "abstract" intelligence, to 
the almost total neglect of "mechanical" intelligence and 
manual dexterity. Italians, on the other hand, have a 
traditional and age-old admiration for manipulative arts 
and crafts. The skill exhibited in the production of a 
beautiful object, a complex object, or an object well 
adapted to its practical use, is held in high esteem and 
encouraged from early childhood. Relatively little em- 
phasis, however, is placed upon the more abstract types 
of talent. 

Even in groups which rank very low on the basis of our 
"iiifelligerice" tests and our cultural standards, specific 
abilities can be found in which they excel markedly. That 
tliHe" differences have not frequently appeared in test 
results is attributable to the fact that the current in- 
telligence tests are a characteristic American development 
and that the testing of racial groups has been conducted 
largely by American psychologists. It is not a very 
difficult matter, however, to construct tests in which an 
apparently "inferior" group makes an excellent showing. 
Thus in the course of an investigation by Klineberg 
(cf. 1 8) among the Dakota Indians, a "beadwork test" 
was devised in which a small sample of beadwork was 
shown to the subjects for four minutes; the sample was 
then removed and the subjects asked to reproduce it from 
memory on a loom, The test was applied to both Whits 


and Indian girls, all of whom were first taught how to do 
beadwork on a loom. As would be expected from their 
greater familiarity with this type of material, the Indian 
girls clearly surpassed the Whites. 

Porteus (25) tried a similar experiment while working 
among the Australian aborigines. Having been impressed 
with the remarkable tracking skill of these people, he 
constructed a test with photographs of footprints, the 
task being to match the two prints made by the same foot. 
On this test, the Australians did practically as well as a 
group of 1 20 White high school students in Hawaii who 
were tested for comparison. In commenting upon these 
results, Porteus remarks : 

Allowing for their unfamiliarity with photographs we may 
say, then, that with test material with which they are familiar 
the aborigines' ability to discriminate form and spatial rela- 
tionships is at least equal to that of whites of high school 
standards of education and of better than average social 
standing (25, p. 401). 

The point is frequently made that racial or national 

wwuJSMJ.. ' . i - , ;" "*"' ' ' " ,**# ' 1'*="**'" ,."-., l ,.- lf j.,".,,i .!>-,, ,,,,, *'Jiv/*t, 

groups can be arranged in a consistent hierarchy if, we 
consHeTTmly" the " higher mental processes." Tests of 
'SS^Wt^^iliiiQSy for example, are considered more 
diagnostic of "intelligence" than those dealing with the 
manipulation of concrete objects or with the perception 
of spatial relationships. The aptitude for dealing with 
symbolical materials, especially of a verbal or numerical 
nature, is regarded as the acme of intellectual attainment. 
The "primitive" man's skill in responding to very slight 
sensory cues, his tal,ents in the construction of objects, 
or the powers of sustained attention and muscular control 
which he may display in his hunting behavior, are re- 
garded as interesting anthropological curios which have, 


however, little or no intellectual worth. As a result, such 
activities have not usually been incorporated in intelli- 
gence scales but have been relegated to a relatively minor 
position in mental testing. 

Upon closer analysis it will become apparent that this 
conception of intellect is itself culturally conditioned. By 
"higher mental processes" is usually meant those aspects 
or segments of behavior which are at a premium in our 
society. Intelligence tests would be very different if they 
had been constructed among American Indians or Aus- 
tralian aborigines rather than in American cities. The 
criterion employed in validating intelligence tests has 
nearly always been success in our social system. Scores 
on the test are correlated with school achievement or per- 
haps with some more general measure of success in our 
society. If such correlations are high, it is concluded that 
the test is a good measure of "intelligence." The age 
criterion is based on the same principle. If scores on a 
given test show a progressive increase with age, it may 
simply mean that the test is measuring those traits which 
our culture imparts to the individual. The older the sub- 
ject, the more opportunity he will have had, in general, to 
acquire such aptitudes. 

Thus it would seem that intelligence tests measure only 
the ability to succeed in our particular culture. Each 
culture, partly through the physical conditions of its 
environment and partly through social tradition, "selects" 
certain activities as the most significant. These it en- 
courages and stimulates; others it neglects or definitely 
suppresses. The relative standing of different cultural 

cluded under the, concept of inteUij^^ 

cultoeln 1 wKirii the test was constructed. 



The point is sometimes made that the vast differences 
in the achievements of various races testify to .their 
dissimilar innate mental equipment. Thus it is argued that 
the differences in cultural achievement among racial 
groups might be a result rather than a cause of such mental 
differences. The cultural milieu in which the individual 
is reared, with its special opportunities and limitations for 
intellectual and emotional development, might itself be a 
reflection of the capacities of each race. The individual of 
a given race might thus be handicapped by poor facilities 
for intellectual development just because his predecessors 
lacked the capacity to produce a more "favorable" 

As evidence of the wide inter-racial variations in 
achievement are cited contributions to the development of 
industry and invention, accomplishments in the realm of 
science, literature, and other artistic productions, com- 
plexity of social and political organization, and many 
other aspects of cultural status. Comparisons have also 
been made in terms of the " eminent" men produced by 
each race. Thus Galton (io 3 pp. 325-337) at one time 
proposed a i6-point scale for estimating the "comparative 
worth of different races" by comparing the relative merits 
of men in each group who had achieved eminence. On this 
basis he suggested, for example, that the Negro is two 
grades lower than the Englishman, and the modern 
Englishman two grades below the Athenian of Greece's 
golden era. 

It should be noted, Jth&k ,&X Argument based upon^the 
relationship between the cultural level and the capacity*of 
races is reversible. On the basis SQlely, of the^ association 
^ to determine 


which Is cause and which is effect. There is therefore no 
reason for concluding ipso facto that racial differences in 
cultural achievement indicate or result from a racial 
difference in capacity. There is considerable evidence, 
on the other hand, which suggests that the cultural differ- 
ences may be responsible for the group differences in 

In the first place, achievement and cultural level are 
frequently found to vary not with race but with environ- 
mental factors. Thus a group which is characterized by a 
given achievement level may be racially very heterogene- 
ous and may constitute a unit only in terms of a common 
experiential background. 1 Secondly, the relative achieve- 
ments of a given group , are influenced by a number, of 
factors which cannot themselves be attributed ito racial 
capacity without stretching the point unduly. The char- 
acteristics of the physical environment, the degree of 
contact with other groups, the discovery of new routes of 
travel and communication, and historical events within 
other groups and thus not within the control of the 
group under consideration have played an important 
part in the cultural development of many societies. 

Thirdly .JTO;^ 

fi;om time to, time. This Is particularly well illustrated by 
some of the ancient African civilizations, such as the 
kingdom of Benin, whose achievements in many fields far 
outstripped the European cultures of the same period. A 
number of "lost arts" of these civilizations represent, in 
fact, abilities which have never been attained in any other 
group. In several cases, the shifts in relative cultural 
level occurred in the absence of any known change in the 
nature of the stock, as might occur through race mixture. 

1 Data bearing on this point will be found in the following chapter. 


Concomitant historical developments can, however, be 
found which might account for the change in cultural level 
Finally, the reader may consider in this connection the 
weight of the evidence from other sources, discussed 
throughout the present book, which indicates the extent 
to which behavioral development depends upon environ- 
mental factors. 


1. Alexander, H. B. "A Comparison of the Ranks of American 
States in Army Alpha and in Social-Economic Status," 
Sch. andSoc., 1922, 16, 388-392. 

2. Arlitt, A. H. "On the Need for Caution in Establishing 
Race Norms," /. AppL PsychoL, 1921, 5, 179-183. 

3. Bagley, W. C. Determinism in Education. Baltimore: War- 
wick and York, 1925. Pp. 194. 

4. Bere, M. A. "Comparative Study of Mental Capacity of 
Children of Foreign Parentage. Teachers College, Columbia 
Univ., Contrib. to Educ.^ No. 154, 1924. Pp. 105. 

5. Blackwood, B. "A Study of Mental Testing in Relation to 
Anthropology," Ment. Meas. Mon., No. 4, 1927. Pp. 120. 

6. Clark, W. W. "Los Angeles Negro Children," Educ. Res. 
Bull., Los Angeles City Schools, 1923, 3, No. 2, 1-2. 

7. Darsie, M. L. "Mental Capacity of American-Born Japa- 
nese Children," Comp. Psychol. Mon., 1926, 15, No. 3, 1-89. 

8. Dodd, S. C. International Group Mental Tests. Princeton 
Univ. Ph.D. Dissertation, 1926. Pp. 101. 

9. Fitzgerald, J. A., and Ludeman, W. W. "The Intelligence 
of Indian Children," /. Comp. PsychoL, 1926, 6, 319-328, 

10. Galton, F. Hereditary Genius: An Inquiry into Its Laws and 
Consequences. London: Macmillan, 1914 (ist ed. 1869). 

Pp- 379- 

11. Garth, T. R. "A Comparison of the Intelligence of Mexican 
and Mixed and Full Blood Indian Children," PsychoL Rev., 

12. Goodenough, F. L. "Racial Differences in Intelligence of 
School Children," /. Exp. PsychoL., 1926, 9, 388-397. 


13. Jamieson, E., and Sandiford, P. "The Mental Capacity of 
Southern Ontario Indians," /. Educ. PsychoL, 1928, 19, 

14. Jones, A. M. "Vocabulary Study of Children in a Foreign 
Industrial Community," Psychol. Clinic, 1928, 17, 13-21. 

15. itelley, T. L. Interpretation of Educational Measurements. 
Yonkers, N. Y.: World Book Co,, 1927, Pp. 363. 

16. Klineberg, 0. "An Experimental Study of Speed and Other 
Factors in 'Racial' Differences," Arch. Psychol, No. 93, 
1928. Pp. in. 

17. - . Negro Intelligence and Selective Migration. N. Y.: 
Columbia Univ. Press, 1935. Pp. 66. 

18. - . Race Differences. N. Y.: Harper, 1935. Pp. 367. 

19. Long, H. H. "The Intelligence of Colored Elementary 
Pupils in Washington, D. C.," /. Negro Educ., 1934, 3, 

20. Mead, M. "Group Intelligence Tests and Linguistic Dis- 
ability among Italian Children," Sch. and Soc., 1927, 25, 

21. McAlpin, A. S. "Changes in Intelligence Quotient of Negro 
Children," /. Negro Educ., 1932, I, 44-48. 

22. Peterson, J., and Lanier, L. H. "Studies in the Compara- 
tive Abilities of Whites and Negroes," Ment. Meas* Mon., 
No. 5, 1929. Pp. 156. 

23. Pintner, R. "Comparison of American and Foreign Chil- 
dren on Intelligence Tests," /. Educ. Psychol., 1923, 14, 

24. Pintner, R., and Keller, R. "Intelligence Tests for Foreign 
Children," /. Educ. PsychoL, 1922, 13, 214-222. 

25. Porteus, S. D, The Psychology of a Primitive People. N. Y.: 
Longmans, Green, 1931. Pp. 438. 

26. Strong, A. C. "Three Hundred Fifty White and Colored 
Children," Fed. Sem., 1913, 20, 485-5 15. 

27. Yerkes, R. M., ed. "Psychological Examining in the United 
States Army," Mem. Nat. Acad. ScL, 1921, 15. 


The comparison of ^cial^^^cultural groups within 
the same population may help to clarify the relative 
coMnFutioii of innate and .epvixonmeiltal factors, in the 
development of group differences. Hjnember,,pf the same 
race can be found,, living under varying cultural conditions, 
and members of different races living within a single w and 
more or less homogeneous cultural group, fruitful cross- 
coiiiparisons can be made. Such a situation is furnished 
by many European nations whose members are drawn 
from more than one of the subdivisions of the Caucasian 
race. Thus it will be recalled that in France may be 
found Nordic, Alpine, and Mediterranean groups, in 
Germany Nordic and Alpine, in Italy Alpine and Mediter- 
ranean. A similar racial heterogeneity is to be found in 
several other European countries. 

The representatives of these racial groups living within 
a single nation are exposed to relatively uniform cultural 
conditions. To a greater or less extent, they share the 
social traditions and customs of their country. Since all 
belong to the "White" race, social distinctions and dis- 
criminations are far less prevalent than is the case with 
Negroid or Mongoloid groups living among Caucasians. 
To be sure the members of each racial group often cluster 
in a certain section of the country. In France, for example, 
the Nordics are found chiefly in northern provinces, the 
Alpines in the central part, and the Mediterraneans in 
the south. Specific differences in economic level, nature of 



occupations, educational opportunities, and other condi- 
tions may and often do exist among the regions inhabited 
by each racial group. Such environmental variations are 
not so large, however, as those found from one nation 
to another, or those which set off the American Negro 
from his White compatriots. I^LJi^^ 
ments of Nordics, Alpines, and Mediterraneans living 
within a single nation are far more similar "than the en- 
vironments of members of the same race, living in different 

V !,, ia , 


In certain cases comparisons have been made between 
narrower and more clearly defined cultural groups, char- 
acterized by common traditions, beliefs, or social and 
educational background. Thus students attending one 
educational institution may be compared with those in 
another, while at the same time racial comparisons may 
be made within each institution. The unit of comparison 
may be a single neighborhood, consisting of a few city 
blocks. This division is particularly well-adapted to a 
large metropolis, such as New York City, in which are to 
be found a number of special national districts, clearly 
differentiated by customs, traditions, and even language. 

djslrig^.maj^^be^compared to 
the ..same racial prnatioaaLarigin 


butliying in a more. typically " American I' -environment. 
Investigations of this nature cannot, of course, offer a 
conclusive analysis of the relative contribution of cultural 
and biological factors. Many uncontrolled conditions 
still remain. Perfect control of conditions, however, can- 
not be obtained outside of an experimental set-up. The 
study of groups in which racial and cultural classifications 
cut across each other at least brings us a step closer to an 
unraveling of the complex of factors which produce 
group differences. 



The testing of the United States army draft during the 
World War furnished the first extensive body of data on 
"intellectual" differences among -immigrant groups in 
this country. In the original report prepared by the army 
psychologists are to be found the distributions of scores 
on Alpha, Beta, and individual intelligence scales for 
12,492 foreign-born men, classified according to country of 
birth (26, Part III, Ch. 6). These data were subsequently 
submitted to a special analysis by Brigham and the re- 
sults published in a book entitled A Study of American 
Intelligence (4). 




(After Brigham, 4, pp. 120-121) 

Country of Birth 

of Cases 

Combined Scale 





14.87 , 















325 * 


















. 4-19 























1 1. 01 






Total foreign-born 



' 1-23 

Native born 





In order to make direct comparisons among individuals 
who had taken different intelligence scales, all scores 
were transmuted into a "combined scale" rating which 
ranged from zero to 25 points. The average and range of 
the combined scale scores of each national group, as well 
as the number of cases, are shown in Table XXIX. The 
reliabilities of the differences between each group and 
every other were computed and showed the majority of 
such differences to be statistically significant. It should be 
noted, however, that the differences are very small and 
the overlapping of groups large. 





(After Brigham, 4, p. 90) 

Years of Residence 

Number of Cases 

Average Score on 
Combined Scale 

o~ c 
6-1 o 

Over 20 





These data were further analyzed in respect to length 

~ wwr _ WBWMBTOWW1sw ^^ W^W *<,>, .-I". ,f, ''jjflv ."-I .,,","" "M<.,'-, ".' n **."*" )',W9MWTW**I* *~* 

of resident j n t j ie United^Slates. Average combined 1 
sc^*^Wes**were computed for men in each residence 
group. All foreign-born men, regardless of country of 
birth, were combined in this tabulation. The number of 
men in each group and their average scores will be found in 
Table XXX. All but one of the differences between the 
residence groups are statistically reliable. After examin- 
ing several alternative explanations, I^righ^^ 

d in average i^td^ig^ce^test score 


from the earliest to the most recent immigrant groups 
indicates a progressive deterioration in the qualit7 of 
immigrants entering the United States. 

Finally an attempt was made to classify the subjects 
into "racial" categories. Tentative estimates were made 
of the proportion of Nordic, Alpine, and Mediterranean 
blood in each country. France, for example, is estimated 
as 30% Nordic, 55% Alpine, and 15% Mediterranean; 
Sweden is listed as 100% Nordic; Roumania 100% Alpine; 
Germany 40% Nordic and 60% Alpine. The distribu- 
tions of intelligence test scores for each national group 
were then cut according to these proportions and re- 
combined into Nordic, Alpine, and Mediterranean groups. 
Thus, for example, all of the Swedish scores were classified 
under Nordic, all of the Roumanian under Alpine. In 
those cases in which more than one racial group is repre- 
sented within a single nation, the average score of that 
national group was allotted proportionately to each racial 
group. Thus 40% of the German sampling was entered 
under Nordic and 60% under Alpine. Since there was no 
way of determining in which portion of the national dis- 
tribution of scores the Alpine and Nordic individuals fell, 
all subjects were given the average score of their respective 
national group. 1 When the scores were combined in this 
fashion, the averages for the three "racial" groups proved 
to be as follows : 

Group Number of Cases ra j e c r * 7 n 

Combined Scale 

Nordic 3456 13.28 

Alpine 4766 1 1 .67 

Mediterranean 4196 1143 

1 It is apparent that this procedure involves a logical fallacy insofar as it 
assumes the absence of differences in score between racial groups within a single 
nationality, and at the same time it undertakes to prove the existence of just 
such a difference among racial groups. 


The difference between these averages are all statistically 
significant, being many times larger than is required for 
perfect reliability. 

In a final evaluation of all of these data* Erigham con- 
ducted' 'thM the differences in intelligence test performance 
found among immigrant groups were racial in character. 
He"Hso r suggested that the decline in score in successive 
residence groups was due to a decreasing immigration 
from the predominantly Nordic countries and an influx 
of Alpine and Mediterranean immigrants. These con- 
clusions have been widely criticized from several angles. 
The representativeness of the immigrant groups as sam- 
plings of their home population has been challenged. The 
adequacy of the tests as instruments for measuring the 
" intelligence" of groups with widely differing educational 
and cultural backgrounds has likewise been questioned. 
The progressive rise in average score with increasing 
length of residence in the United States may itself be due 
in large measure to the influence of environment. Lan- 
guage handicap, furthermore, was not ruled out. In fact 
a comparison of English-speaking and non-English- 
speaking "Nordics" revealed a reliable difference in 
favor of the former, although the non-English-speaking 
Nordics still surpassed the Alpine and Mediterranean 
groups. Finally the allocation of a certain proportion of 
each national group to one or another "race" can but 
serve to confuse the issues. Since no differentiation was 
made among members of different races within a^ single 
national group but the subjects were chosen indiscrim- 
inately from the entire distribution of national scores, 
nothing was gained by the reclassification. 

It might be added that in a subsequent publication 
(5) Brigham himself has withdrawn completely from his 
earlier position. On the basis of recent findings on mental 


organization and their bearing upon the interpretation of 
test results, he concludes: 

If the Army Alpha test has thus been shown to be internally 
inconsistent to such a degree, then it is absurd to go beyond 
this point and combine alpha, beta, the Stanford-Binet and 
the individual performance tests in the so-called "combined 
scale," or to regard a combined scale derived from one test or 
complex of tests as equivalent to that derived from another 
test or another complex of tests. As this method was used by 
the writer in his earlier analysis of the army tests as applied 
to samples of the foreign-born in the draft, that study with 
its entire superstructure of racial differences collapses com- 
pletely (5, p. 164). 

In^spite of its criticism by psychologists and anthropolo- 
gists, however, Brigham's book has been widely quoted 
and has proved very influential in determining popular 
opinion on questions of race and immigration. J^t is 
chi^fijJoT a , r tlnsjeason, s^at^^p analysis of the, main. conchT- 
siops put forth in this booK has been included in the 

The most direct interpretation which can be put upon 
the army data themselves is that they indicate the relative 
standing of contemporary immigrant groups in the 
United States on certain specific tests. These tests were 
so constructed as to be more or less valid indices of suc- 
cess in our particular society, calling into play those char- 
acteristics or segments of behavior which are valued in our 
culture. At the same time the subjects approached the 
tests with a background of early training and environ- 
ment which may have varied widely from one national 
group to another and which was probably reflected in 
their responses. Envisaged in these terms, the army data 
have been amply corroborated by subsequent studies. 
The testing of American-born schoolchildren of immigrant 


parents has In general yielded the same rank order of 
national groups as was found in the army draft. Jjjfisreral 

TSOS'Qkpf -testa, report abouttjie 

mte^ .relative^ t standing_for_ r the, different,, jaatiQa,ai,,grougs 
in lh]s w Qiantry ? ^although the,., actual, amQunt ,ol difference 
varies v ^ith the nature of the test and other factors. 1 


jHQie , .empirically 

s, macle by Hirsch (i4Un at ,an ^investi- 
gation of children of immigrants in the United States. 
The main group of subjects consisted of 4983 Massachu- 
setts public school children ranging in age from 5^ to 18 
and in school grade from the first to the ninth. In social 
and occupational level the group was quite homogeneous, 
all of the subjects living in small manufacturing com- 
munities. There was no segregation of national groups 
into districts and all of the children attended the same 

The Pintner-Cunningham Primary Scale was given to 
all first grade children. This is a non-verbal picture test 
in which the directions are, however, given in oral Eng- 
lish. The children in grades 2 and 3 were examined with 
the Dearborn Test A and those from grade 4 upwards 
with the Dearborn Test C. The former test is largely 
non-verbal in its content, the latter about half non- 
verbal Thus an effort was made to minimize the influ- 
ence of language handicap by the selection of these tests. 
The role of speed was also reduced by allowing a longer 
time limit on all tests than is specified in the standard 
directions. The children were first classified into national 

1 For a good summary of such studies prior to 1926, the reader is referred to 
Kirkpatrick (16). Cf. also Berry (2), Brown /6), Feingold (10), Goodenough 
(13), Hirsch (14), Murdock (22), Young (27). 



groups on the basis of parents' birthplace. An "American" 
group of native parentage was also included for compara- 
tive purposes. 

The results of this analysis are shown in Table XXXI. 
Most of the differences between the average I.Q.'s of these 
natiohargrdups were statistically reliable. The same rank 
order of nationalities was obtained when the groups were 
compared in the percentage of " very superior intelligence" 
and of "borderline deficiency." The relative status, of 
the national groups also agreed in general with that re- 
ported by previous investigators. 


(After Hirsch, 14, p. 287) 


of Cases 



of Cases 


Polish Jews 



British Canadians 





102. 1 










Russian Jews 















French Canadians 







6 7 I 





Taking the national groups as a whole, Hirsch found 
no evidence in support of the so-called " Nordic myth." 
There seemed to be no very close connection between 
high LQ. and the possession of "Nordic blood." Thus 
among the eight highest entries in Table XXXI are to be 
found two predominantly Nordic groups (English and 
Swedes), two which are largely Alpine (Germans and 
Lithuanians), one Mediterranean (Irish), two Jewish 
(Polish and Russian Jews), and one composite group 


In order to arrive at a somewhat more accurate de- 
termination of "race/ 5 .Hirsch classified each individ- 
ual into a racial type on the basis of eye and hair color. 
All subjects, irrespective of their national descent, were 
dffi3H"Jnto three major categories :, the "blond type" 
withjight hair, and blue, gray, or hazel eyes; the "bru- 
nette tyge" with black hair and gray,, hazel, brown, or 
Black eyes; and the "mixed .typt?. exhibiting all ..other 
combinations of hair and eye color. The blond type was 
taken to correspond roughly to the Nordic and the 
brunette to the Mediterranean race. The mixed type 
would of course include Alpines as well as mixtures of 
any of the three racial stocks. This method of classifi- 
cation is, to be sure, crude. Hair and eye color are not 
generally considered to be very reliable criteria of race. 
The analysis is, however, suggestive as a first attempt in 
the direct classification of individuals into racial categories. 

In Table XXXII will be found the number of cases 
and the average LQ. of blond, mixed, and brunette types 
within each national group. 1 These data lending support 
to ^raci^j^ej^retation of group differences. No one of 
the thi;^pj^^ consistently superior or inferior 

within all^ n 3 ^tiQQ,g][, r gTOiap^ Thus among the representa- 
tives of one nation the blonds stand first; among those 
of another nation the brunettes lead. The differences 
among physical types, furthermore, are much smaller 
than those within a single type. The differences in LQ. 
between any two types within a single nation range from 
o.i for French Canadians to 6.7 for Poles. The differences 
between the lowest and highest national averages within 
any one physical type, on the other hand, are all larger. For 
each of the three types, these differences are as follows: 

1 One national group, the Scotch, has been omitted because of the small num- 
ber of cases tested, although Hirsch includes it in his "racial" analysis. 



Physical Type 



Largest LQ. Difference 

within Physical Type 

among National Groups 



National Groups 

English and Poles 
Polish Jews and 

English and 


These cross-comparisons between national and "racial" 

cfaFegpr'ies suggest that the obtained' differences '' re 
closely linked with nationality than with racial background. 



(After Hirsch, 14, p. 333) 

National Group 

Blond Type 

Mixed Type 

Brunette Type 


Aver. LQ. 


Aver. LQ, 


Aver. LQ. 










I O6. 2 





British Canadians 







French Canadians 






































1 02 











Polish Jews 




















Russian Jews 














Curiouslj^nough Hirsch's own. interpretation of these 

connection he proposes a ^N^o^ScM^^ypoihtsis'" 
which is essentially a suggestion for the ^classification 


of subgroups within the Caucasian race. The division 
into Nordic, Alpine, and Mediterranean he considers out- 
worn. Hirsch's contention is that although these may 
have represented the original stocks, new racial units 
have been built up through such influences as migration, 
interbreeding, and natural selection. These units cor- 
respond to many of our modern nations, such as England, 
France, Germany, Italy, Spain. 1 According to Hirsch 
"each distinct nation may be regarded as a psycho- 
biological species which constitutes and fabricates a social 
milieu that is congenial to and is an expression of its 
innate psychic structure" (14, p. 374). 

Jt^might be noted that if present-day national groups 
have become crystallized into distinct " natio-races " or 
bioTogicargroTips, we "sEouid ,ezpect , the , members of such 
grQUps to manifest distinctive phy^lpai^ ^ell. as mental 
chaacteristics. But allhc 

range of variation "within any one nation with, marked 
overlapping, between^nations. "Tfie members of a given 
nation cannot be identified on the basis of physical dif- 
ferentia and do not therefore constitute a "race" in the 
biological sense. There is, furthermore, no need to hy- 
postatize " natio-races " in order to explain the behavioral 
similarity of members of a single nation. Thejcuhujral 

evidence to account for their XQJBmum^ 
their differences i 


Regardless of theyjarticula^^ 


1 Thfs correspondence is not considered to be perfect, however, since some 
nations which, are at present political units are composed of distinct "racial" and 
cultural groups. Several of the Balkan countries are examples of this. 


In showing that group differences tend to be larger when 
individuals are classified according to nationality than when 
they are classified according to physical resemblance. This 
conclusion, however, is subject to two limitations. In the 
first place, the data were obtained exclusively on the chil- 
dren of immigrant groups in the United States. Thus the 
samplings employed may not have been representative of 
their national populations. Secondly, the physical criteria 
employed to classify the subjects into "racial" groups are 
open to criticism and the resulting categories are very crude 
approximations of the three racial subgroups of Europe. 

Both of these limitations were avoided in SL, study by 

KlineBefg"~(T7],",fii. which the .attempt, was made to obtain 
as pure samples as possible of the three f E,mQp<|n races 
in Europe. In order to permit cross-comparisons of na- 
tional and racial groups, the investigation was conducted 
in three countries which are heterogeneous in racial 
composition. The subjects were 10- to 12-year-old school- 
boys in rural sections of Germany, France, and Italy. 1 The 
samples were taken from those geographical areas in 
which, according to maps of the distribution of various 
physical traits, pure types of each race were most likely 
to be found. Only children who had themselves, as well 
as their parents, been born in each particular area were 
included in the study. The subjects were further selected 
on the basis of three physical criteria: eye color, hair 
color, and cephalic index. No subject was employed unless 
he fell within the specified limits for his race in all three 
criteria. The groups were comparable in economic, social, 
and occupational level, the differences among them in 
these respects being relatively slight. 

1 Rural groups were chosen since too much intermixture had occurred in urban 
districts to yield a sufficient number of "pure types." Three city groups in 
Hamburg, Paris, and Rome were also tested for comparative purposes. The 
results of this testing will be reported in the following chapter. 


Each subject was examined individually with a short 
performance scale consisting of six of the Pintner-Paterson 
tests. 1 These tests are all non-verbal and involve the 
manipulation of objects. Brief oral directions were given 
in the subject's native language. Performance was scored 
in terms of speed as well as accuracy. In Table XXXIII 
will be found the average, median, and range of scores 
within each group. The geographical location of the group 
and the number of villages covered are also given. The 
number of cases is exactly 100 in each of the seven groups. 



(After Klineberg, 17, p. 27) 



Number of 

Performance Scale Scores 




I. German Nordic 






2. French Medi- 








3. German Alpine 





80-2 I I 

4. Italian Alpine 






5. French Alpine 


and Velay 





6. French Nordic 






7. Italian Medi- 







TheeJHplts s k w racked variations among different 


Alpine-Mediterranean hierarchy is not mjinta,inf d. Al- 

^* i ~'~~~><w^^ i *n * . n.a,l, I / Ji "* ."!.?** i "' Jt '** r '**' ' f r r ^" fr ^* mm '* "'"mm 

though the highest^avefage score is obtained by a Nordic 
group, the highest median is found in a Mediterranean 
group. Similarly, the rank-order of the racial groups 

1 The Knox Cube, as well as the Triangle, Healy A, Two-Figure, Five-Figure 
and Casuist form boards. 


within any one nation is inconsistent. Thus in France 
the Mediterranean group is best, the Alpine intermediate, 
and the Nordic poorest; whereas in Germany the Nordic 
is superior to the Alpine sampling, and in Italy the Alpine 
is superior to the Mediterranean. The marked overlapping 
of groups, as indicated by the range, should also be noted. 
When all Nordics, Alpines, and Mediterraneans are com- 
pared, regardless of nationality, the following average 
scores are obtained: 

Nordic 188.5 

Alpine 187.5 

Mediterranean 185.2 

None of these differences is statistically reliable. The 
variation from one Nordic sample to another, on the 
other hand, is large and reliable. The same is true of the 
other two racial groups. Thus there is a difference of 
24.4 points between French and Italian Mediterraneans; 
one of 19.4 points between German and French Nordics; 
and one of 13.4 between German and French Alpines. 

These results clearly show that the differences among 
nationaT"]gr^ , , 

composition, of the "jpiircentage of Nordic, Alpine, and 
Mediterranean " blood '^in.eaup^ppj^rjr. Because of the 
variations found among different samples of the same 
nation, Klineberg proposes that the differences may not 
even be national in scope but should be envisaged in 
terms of smaller cultural units. Thajjthejd^^ are 


is suggested by two considerations. In the first place, the 

^<^---^^ . ^.,. ,*-,., *, 

pre4ommance of a single inbred family strain in any one 

J- ^""''""''"^^"^^ ~ '*""* ' Y'*" / >< - * - ',><. ,-,,, ;, 

of tiae^amplings tested is ., v<piy v ,unUkdbpbeeau8 of the 
wide jarea covered. It will be recalled that from 9 to 19 vil- 
lages were canvassed for each single sampling. Jfajthe 
second place, very interestin^^arallelisms were found 


. regipn^ and Ji& ( intelligence test performance* of 
its Inhabitants. 


Owing to the relatively recent advent of personality 
tests in the field of mental measurement and to the com- 
plexity and elusiveness of personality traits, very little 
objective information is available on racial and national 
differences in these traits. Pogu^^ 
hand, has consuslte^ 

nientaT^^ Group differ- 

ences in personality are considered to be even greater 
than in intelligence, and the belief in such emotional 
differences persists even when intellectual equality is 
granted. It is relatively difficult to challenge the existence 
of racial differences in personality because of the frequency 
with which such differences are apparently demonstrated 
in everyday observation. The Irish wit, the excitability 
of the South European, the easy-going nature of the 
Negro, the stolidity of the American Indian, the composure 
of the Englishman, and a host of similar characterizations 
have all become a part of our daily vocabulary. 

Statements have frequently been made in regard to the 
predisposition of various racial groups to crime (cf., e.g., i). 
Thus the large percentage of crime in the United States 
has been attributed by some to the influx of certain 
classes of immigrants into our country. Statistics have 
been cited to show the greater frequency of crime among 
Negroes and among immigrants from eastern and southern 
Europe than among the native-born White population. 

Figures often lie, and in the interpretation of crime 
statistics it is particularly difficult to disentangle the 


many uncontrolled factors which confuse the issue. Among 
such factors may be mentioned the inequality in arrests 
and convictions among various groups; Negroes and "for- 
eigners," for example, are more readily arrested "on 
suspicion" and on less grounds than is in general required 
for native-born Whites. The fact that most foreigners are 
adults would also give them a disproportionate percentage 
of crime if they are compared with the figures for native- 
born persons of all ages. Similarly, foreigners are more 
often city-dwellers and live in poorer social and economic 
conditions than native-born Americans, all of which is 
conducive to crime. The foreigner, furthermore, may 
have brought with him traditions which happen to conflict 
with the accepted standards in our country. Finally, 
the maladjustment which ensues from adaptation to a 
new culture will have its effect upon first and second 
generation immigrants, although the nature of this effect 
probably differs in the two generations. In spite of the 
many factors which load the dice, a,g^ijast u The, .fprQign- 
^^j^jj'-^^^^g^^jg^jpg^ r ecent careful analyses QJLtJie 
dat&IglLaaiiv^ of 

age have faikeLto, reveal,^ higher ,rate of ^arj"s1;v CQAvic- 
tiqns ai , i pi;,,g9,pamil:me^ts among the foreigja-bprn (cf. 25). 
The same may be said in regard to statistics on insanity 
among different racial or national groups (cf., e.g., 20). 
Most of the conditions which render the evaluation of 
crime statistics difficult also affect the data on insanity. 
In addition may be mentioned the factor of hospitaliza- 
tion. Institutional subjects may not be a representative 
sampling of the actual cases of mental disorder in differ- 
ent groups. Thus the opportunities for hospital care 
are not equal for such groups as Whites and Negroes in 
certain parts of the country. On the other hand, because 
of economic conditions, certain groups are better able to 


care for the mentally disordered persons at home, thus 
eliminating the necessity for hospitalization. In regard 
to the predisposition of certain racial groups to a particular 
form of insanity, the results have been entirely negative. 1 

The application of personality tests to various groups 
has yielded results which are almost equally difficult to 
interpret. Most of these studies have been conducted 
on the American Negro (cf. 3, 7, 15, 23, 24), although 
some data on Oriental (8), American Indian (12) and 
European immigrant groups (n, 21) are also available. 
The doubtful reliability and validity of many personality 
tests reduce the significance of the results which have 
been obtained. Some investigators have found no reliable 
difference among the racial or national groups compared. 
Others have obtained slight differences in the direction 
expected from tradition and popular belief. In this con- 
nection environmental conditions and especially the force 
of "social expectancy" in determining the development 
of personality traits cannot be ignored. What is expected 
of an individual frequently determines what he will do, 
especially if such expectation is manifested early and 

In a more recent investigation (19)^ the problem s of race 
an4j^rsonaLlit5r" i ^'^ .analyzed more directly . Jaj^ (i) Jzhe 
use of more re][lal:)l^^d-ca^fifully standardized .pqrjapnality 
tests; (2) the classification of racial groups on the basis 
^accepted ^jsical^pF^ilt; and (3). cross-comparisons 
^^^^^^^ ^^ ig ^ diyiskms wittiA,thft,^3UpSUpn- 
plpjecL' Over 400 male and female students attending 
eight different institutions of collegiate rank in New York 
City and its environs were examined with a series of 
personality tests. The tests included the Bernreuter 
Personality Inventory scored for six "traits," the Allport- 

1 C* Klineberg (18), Ch. XIII for a summary and discussion of this material. 


Vernon Study of Values, an honesty test (Mailer Test 
of Sports and Hobbies), and two tests specially devised 
for use in this investigation, one to measure suggestibility 
and the other persistence. 1 The subjects were classified 
into Nordic, Alpine, and Mediterranean groups on the 
basis of cephalic index, eye color, hair color, and skin 
color. In general if all but one of these criteria pointed 
to a certain group, the subject was placed in that group. 
If, however, one measure was far out of keeping with the 
limits set for each group, or if more than one measure 
fell even slightly beyond such limits, the subject was 
omitted from the classification. By this method it was 
possible to obtain approximately 50 men and 50 women 
in each of the three racial groups. 

The average scores of Nordic, Alpine, and Mediter- 
ranean groups on each test are given in Table XXXIV. 
The data for the two sexes have been reported separately. 
On the Allport-Vernon Study of Values, only one of the 
differences is significant in each of the sex groups. Among 
the women there is a reliable difference between Mediter- 
raneans and Alpines in the score for "aesthetic value." 
This difference is 3.26 times as large as its standard error, 
the higher average occurring in the Mediterranean group. 
Among the male students a reliable difference was, found 
between Nordic and Alpine groups in the score for "re- 
ligious value." This difference was in favor of the Nordics, 
the critical ratio being 4.64. Upon further analysis, 
both of these differences seemed to be rather closely 
linked up with institutional groupings. Thus the highest 
average score for "religious value" was obtained in a 
Catholic college for men in which were found only three 
Alpines. This would tend to pull down the average of the 

1 For a fuller discussion of these tests, the reader is referred to Chapter IX, in 
which another part of the same investigation was reported. 




(After Klineberg, Fjcld, and Foley, 19) 1 

















(N-6 4 ) 



Allport-Fernon Study of 


I. Theoretical 







2. Economic 







3. ^Esthetic 







4. Social 







5. Political 







6. Religious 

33 .86 






Bernr enter: 

i . B iN : Neuroticism 







2. B 2 S: Self-sufficiency 







3. Bsl: Introversion 






- 7.91 

4. B4D: Dominance 


3 6 -73 





5. FiC: Self-confidence 


- 2,14 



- 7.37 


6. F 2 S: Sociability 

7 .85 













Persistence * 







Honesty * 







*Not all subjects were given these tests. 

Alpine group in relation to those of the other two "racial" 
classes. Similarly, among the female subjects, the highest 
scores in "aesthetic value " were obtained in an institution 
which encourages the aesthetic attitude, as is evidenced 
by a large and popular art department. This institution 
furnished a relatively large number of Mediterraneans, 
thus raising the average "aesthetic value" score of the 
latter group. None of the other Allport-Vernon scores 
yielded reliable differences between racial groups. 

i The writer is indebted to Drs. Klineberg, Fjeld, and Foley for making avail- 
able to her the unpublished data of this investigation. 


None of the differences on the six Bernreuter scores 
proved to be statistically reliable in either male or female 
group. All of these critical ratios are less than three. 
Likewise, in the three remaining tests, i.e., suggestibility, 
honesty, and persistence, no significant group differences 
were found. 

It is apparent that in the personality traits measured 
in this sluHyTTiEe differences among Nordics, Alpines, and 
Mediterraneans within college samplings are very slight. 
Nor can it be argued that the lack of differentiation among 
these groups was due to the. homogeneity of college stu- 
dents in the characteristics under investigation. Although 
relatively homogeneous in intellectual traits, college stu- 
dents exhibit large individual differences in personality 
development. This is borne out by the very wide ranges 
and S.D.'s found within each group. It may also be men- 
tioned that as a result of the wide range covered by each 
group, a larjjej.n<^ the 

distributions of Nordics,, A]pines^,$^ was 

obtained on each test. 

Since the academic institutions included in this survey 
differed from each other in a number of important re- 
spects, a comparison of subjects from each institution 
was believed to be of some interest. Although all of these 
institutions offer courses of collegiate level, they vary 
widely in the social and economic status of their student 
body as well as in the specific attitudes which they 
traditionally foster. Thus two institutions draw their 
students very largely from wealthy and socially prominent 
families. In several the student body comes from the 
upper middle class, thus being more nearly typical of the 
general college population. In one school the majority 
of the students fall into the "laboring" and lower middle 
classes, and are definitely of a lower social and economic 


level than the other groups. One institution is a Catholic 
college with a strongly religious tone in all of its academic 
work. At least two of the academic groups, on the other 
hand, are notoriously agnostic and foster a very critical 
attitude towards all religions. Equally pronounced differ- 
ences are to be found in radicalism and conservatism, in 
the relative emphasis placed upon the scientific and the 
aesthetic approach, and in other attitudes characteristic 
of each institution. 

In sharp contrast to the generally insignificant differ- 
ences found between racial groups, large and reliable 
differences in average score were frequently obtained 
between institutions. Several of these differences were 
many times larger than is required for complete statis- 
tical reliability. In both male and female samplings, 
the Allport-Vernon scores showed the largest differences. 
These differences tallied closely with well-known char- 
acteristics of the institutions under consideration. Thus 
in "religious value," the Catholic college obtained the 
highest average score and a traditionally radical, agnostic 
group of low economic status obtained the lowest, the 
difference being 14.49 times as large as its 'standard error. 
It is interesting to note that another very large difference 
was obtained between these same two groups in "the- 
oretical value." In this case, however, the difference was 
in favor of the latter group, the critical ratio being 7.18. 
On the Bernreuter scales the differences were not so 
marked, although many were statistically reliable. The 
tests of suggestibility, honesty, and persistence yielded 
relatively small and unreliable differences. 

In summary, it will be noted that difference ampng the 
thre^nraSaTgroups' tencled to be small and unreliable, 
whereas tfiose among ^ institutjra 
larger "and , V^ Whatever the cause 


of these institutional differences, it cannot be "race" in 
the biological sense, since the differences disappear when 
individuals are classified according to the physical criteria 
of race. The explanation of these personality differences 
from one institution to another is not difficult to find. 
In the first place, selection obviously op